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Frontiers in Developmental Psychology ·

Volume 4 - 2026 | https://doi.org/10.3389/fdpys.2026.1866997

Reducing aggression and peer victimization in elementary classrooms: efficacy of the meet up and buddy up interventions

  • Ashley R. McDonald1
  • Haining Ren2
  • Sabina Low1,2*corresponding author
  • Laura D. Hanish1,2
  • Richard A. Fabes1,2
  • Carol Lynn Martin1,2
  • Cindy Faith Miller3
  • Lorey A. Wheeler4
  1. 1T. Denny Sanford Harmony Institute, Arizona State University, Tempe, AZ, United States
  2. 2T. Denny Sanford School of Social and Family Dynamics, Arizona State University, Tempe, AZ, United States
  3. 3Department of Counseling, Leadership, Adult Education and School Psychology, Texas State University, San Marcos, TX, United States
  4. 4The Nebraska Center for Research on Children, Youth, Families and Schools, University of Nebraska–Lincoln, Lincoln, NE, United States
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Abstract

The current study evaluated the efficacy of the Meet Up Buddy Up (MUBU) intervention, designed to promote positive classroom relationships among diverse groups of peers, in reducing aggression and peer victimization among 4 th -grade students, with a focus on how gender and race/ethnicity moderated intervention effects. Using a randomized controlled trial (RCT), MUBU was evaluated with 346 4 th graders (53.5% girls; 54.9% White) by comparing students in intervention classrooms with students in control classrooms on measures of aggression and peer victimization. Our findings supported that MUBU effectively attenuated increases in aggression and victimization, and race/ethnicity was a significant moderator of the intervention's effects, while gender did not significantly influence the results. MUBU represents a promising strategy for improving peer dynamics.

Keywords

Introduction

Peer aggression is a significant and persistent challenge in childhood. Despite decades of attention, aggressive behavior, defined as intentional behavior aimed at causing harm to a peer (Crick et al., 1997) and peer victimization, the experience of being targeted by such behavior (Card and Hodges, 2008), remain disturbingly common in childhood (Ariani et al., 2025; Casper and Card, 2017). Peer relationships play a crucial role in the development and maintenance of aggressive behaviors and victimization (Card et al., 2009; Salmivalli, 2010). A large body of research demonstrates that children who have positive peer experiences have relatively low rates of involvement in aggression, as both aggressors and victims (Hodges and Perry, 1999; Werner and Crick, 2004). In contrast, experiencing negative peer relationships contributes to the emergence of aggressive behavior and victimization, which are often associated with long-term challenges in social, psychological, and academic adjustment (Campbell et al., 2006; Card and Little, 2006; Casper and Card, 2017; Ladd et al., 2017; Reijntjes et al., 2010, 2011; Schwartz et al., 2005).

Peer relationships in childhood are shaped by similarity (i.e., homophily), with children tending to affiliate with peers who share similar demographic characteristics (e.g., gender and race/ethnicity) and behavioral tendencies, including aggression and victimization (Rubin et al., 2005). A lack of interaction with dissimilar peers, in terms of demographic characteristics, has been shown to reinforce intergroup stereotypes, maintain existing social hierarchies, and contribute to exclusionary practices that underlie peer aggression and victimization (Graham, 2006; Killen et al., 2013; Martin et al., 2014). Additionally, behavioral similarity plays a critical role in peer affiliation processes. Children who engage in aggressive behaviors are likely to associate with similarly aggressive peers, fostering peer group norms that validate and perpetuate aggression (Deptula and Cohen, 2004; Werner and Crick, 2004). Similarly, youth who are frequently victimized tend to form relationships with others who share similar victimization experiences, which can reinforce social isolation and reduce access to protective peer networks (Ellis and Zarbatany, 2007; Lodder et al., 2016; Scholte et al., 2007). Thus, the absence of positive interaction across diverse peer groups, both demographically and behaviorally, can entrench patterns of aggression and victimization, highlighting the importance of social integration in mitigating the emergence of aggression.

Thus, to reduce aggressive behavior and victimization in childhood, it is essential to promote positive peer relationships and support children's social integration with diverse peers (Fabes et al., 2019; Kawabata and Crick, 2011; Killen et al., 2013; Saarento et al., 2015). Middle childhood represents a particularly important developmental period for these efforts, as children's socio-cognitive skills are maturing, peer relationships become increasingly salient, and social networks expand (Maunder and Monks, 2019; McHale et al., 2003). This stage is also marked by the growing stability of aggression and victimization patterns, with aggressive behavior becoming more entrenched and victimized children facing greater social marginalization (Adams et al., 2005; Camodeca et al., 2002; Demol et al., 2022). Thus, middle childhood offers a critical window for intervention to foster healthier peer interactions and prevent long-term maladjustment. In this study, we look at the impact of Meet Up and Buddy Up (MUBU; Miller et al., 2025; Xiao et al., 2023), two universal, easy-to-implement classroom interventions designed to promote positive intergroup peer relationships, on childhood aggression and victimization.

Peer relationships and aggression and victimization

Peer relationships in school play a central role in children's engagement in aggression—either as perpetrators or victims. Classrooms are the primary contexts for peer relationships in elementary school, in which relations operate at both the dyadic and broader classroom and peer-group levels (Rubin et al., 2015). At the dyadic level, repeated, supported positive interactions among individual classmates promote familiarity and trust and are the basis for friendship. At the classroom level, shared norms of inclusion and respect can shift the broader social climate, decreasing tolerance for aggression and exclusion (Chang, 2004; Hodges et al., 1997; Hong and Espelage, 2012; Mouttapa et al., 2004). Both types of relationships are associated with children's aggression and victimization (Hodges et al., 1997; Hong and Espelage, 2012; Mouttapa et al., 2004).

Dyadic relationships: friendship

At the dyadic level, friendships are important for understanding peer victimization and aggression. Friendships provide children with security, protection, and emotional support; opportunities to learn socioemotional skills such as empathy, emotion regulation, and constructive conflict resolution; and shared behavioral norms that influence behavior (Bukowski, 2001; Rubin et al., 2015). These processes and skills are crucial to reducing peer victimization and aggression (Hodges et al., 1997, 1999; Salmivalli, 2010). Empirical evidence consistently indicates that children who experience peer victimization tend to have fewer friendships than non-victimized peers (Hodges et al., 1997; Hodges and Perry, 1999; Mouttapa et al., 2004; Salmivalli et al., 1997; Serdiouk et al., 2016), and chronic victimization is less common among children who have many friends (Hodges et al., 1999; Romera et al., 2021). Research suggests that friendships buffer against peer victimization by offering emotional and instrumental support, advice on handling peer conflicts, and psychological resilience needed to cope with or repel aggressive encounters effectively (Adams et al., 2011; Bukowski et al., 2010; Hartup and Stevens, 1997; Hodges et al., 1999). Taken together, studies suggest that limited positive friendship connections reduce access to the positive aspects of friendship that buffer against victimization and the development and reinforcement of aggression.

Behavioral similarity plays a particularly salient role in friendship formation and maintenance. Children who experience chronic peer victimization are more likely to form friendships with others who share similar victimization experiences (Hodges et al., 1997; Salmivalli et al., 1997; Scholte et al., 2007), which may unintentionally reinforce social isolation, limit access to protective peer networks, and contribute to the persistence of victimization. Similarly, children who engage in aggressive behaviors are more likely to associate with similarly aggressive peers, fostering peer contexts that normalize and reinforce aggression (Hong and Espelage, 2012). Longitudinal research highlights the socializing effects of friendship composition. Studies have found that aggressive youth who affiliate with aggressive peers tend to remain aggressive over time, while aggressive youth with non-aggressive friends show significant reductions in aggression, without corresponding increases in aggression among their non-aggressive peers (Adams et al., 2005; Hektner et al., 2003; Warman and Cohen, 2000). Similarly, Hodges et al. (1999) found that victimized children with at least one non-victimized friend were less likely to experience increases in victimization over time, and these friendships did not increase risk for the non-victimized peers, highlighting their protective and socially safe role.

Classroom level peer dynamics

Peer aggression and victimization are best understood within the broader context of peer group dynamics rather than as isolated interactions. Children are embedded in classroom social networks, which are small-scale social systems in which peers interact regularly and mutually influence one another (Ahn and Rodkin, 2014; Rodkin and Gest, 2010). Within the classroom peer ecology, children's social status, the structure of peer relationships, and shared norms jointly shape peer aggression and victimization (Ahn and Rodkin, 2014; Hodges et al., 1997; Mouttapa et al., 2004; Sentse et al., 2015). Victimized children are typically less liked by their peers and experience peer rejection, which is a robust risk factor for both aggression and victimization, as rejected youth are more likely to be perceived as safe targets and experience escalating exclusion over time (Hodges and Perry, 1999; Ladd and Troop-Gordon, 2003; Salmivalli, 2010). In contrast, peer acceptance serves as a protective factor by providing access to social support and prosocial interactions (Hodges et al., 1997; Hodges and Perry, 1999; Kawabata et al., 2014). The social positioning of aggressive children is more heterogeneous: although many are disliked, a substantial subset attains high status or popularity, indicating that aggression can function as a socially adaptive strategy in some classroom contexts (Andrews, 2023).

Classroom-level social integration, cohesion, and norms further shape the occurrence and maintenance of aggression and victimization. Research suggests that classrooms that are more cohesive and integrated have lower levels of aggression and victimization (Ahn et al., 2010; Ahn and Rodkin, 2014; Garandeau et al., 2011; Schäfer et al., 2005). Hierarchical classroom structures concentrate social power and are associated with higher levels of bullying and more persistent victimization (Ahn et al., 2010; Garandeau et al., 2011; Schäfer et al., 2005). In contrast, cohesive and egalitarian classrooms tend to show lower levels of aggression and victimization, likely because social roles are more fluid and peer relationships are more inclusive (Ahn and Rodkin, 2014). Classroom norms also directly influence peer behavior: when aggression is common or implicitly accepted, it becomes a legitimate means of achieving or maintaining status, thereby increasing overall levels of aggression and victimization (Chang, 2004; Garandeau et al., 2014). Conversely, classrooms characterized by strong prosocial norms discourage aggressive behavior and promote peer support, contributing to lower rates of victimization and a more positive social climate (Laninga-Wijnen et al., 2020).

Overall, these findings underscore the need for interventions that operate simultaneously at both the dyadic and classroom group levels. Because aggression and victimization emerge through ongoing peer interactions embedded within classroom social networks, approaches that focus solely on individual children, specific dyads, or isolated incidents are unlikely to produce sustained effects (Swearer et al., 2012). Teachers are uniquely positioned to shape classroom social dynamics through everyday instructional and management practices, thereby influencing both peer relationships and broader group processes (Gest and Rodkin, 2011). Accordingly, effective prevention efforts should simultaneously support positive dyadic relationships and address social integration, classroom-level norms, and patterns of peer interconnectivity that contribute to aggression and victimization (Saarento et al., 2015).

Current approaches

In middle to late childhood, interventions targeting peer relationships typically focus on enhancing social-emotional competencies, providing structured peer support, and creating opportunities for cooperative engagement. School-based social-emotional learning (SEL) programs teach skills such as emotion regulation, perspective-taking, empathy, and constructive conflict resolution, often through multi-week classroom lessons or small group sessions, and consistently improve prosocial behavior, peer acceptance, and classroom connectedness (Durlak et al., 2011; Taylor et al., 2017). Although peer-relationship interventions generally improve social skills and friendship quality, their effects on aggression and peer victimization are often mixed (Pollak et al., 2023). Some programs demonstrate reductions in physical aggression and improvements in prosocial behaviors, whereas effects on relational aggression, bullying, or victimization are frequently modest or non-significant (Merrell et al., 2008; Miller et al., 2017; Ttofi and Farrington, 2011). These mixed effects are closely linked to the limitations of these interventions. Dyadic- and small-group interventions strengthen skills within targeted relationships but rarely shift classroom-wide norms, limiting reductions in broader patterns of aggression and victimization. In a meta-analysis that found that social skills interventions alone are not sufficient to reduce bullying (Silva et al., 2018), the authors suggested that bullying as a group phenomenon needs to be addressed by interventions targeting group norms and group processes beyond individual social behaviors (Silva et al., 2018). Peer relationship interventions for children with behavioral or emotional risk factors might need to go beyond content delivery and skills practice.

Furthermore, these interventions may cluster high-risk children together, inadvertently reinforcing aggressive behaviors through peer contagion (Dishion et al., 1999). Classroom-level programs may improve overall social climate but often provide limited opportunities for children to interact directly with a variety of peers, reducing chances to generalize prosocial skills across diverse relationships and limiting effects on aggression and social isolation (De Mooij et al., 2020; Farmer et al., 2019; Merrell et al., 2008). Additionally, many programs are time- and resource-intensive, require trained facilitators, and vary in duration and implementation fidelity, which constrains scalability and consistent impact across settings (Pollak et al., 2023).

Meet up and buddy up

The Meet Up and Buddy Up (MUBU) strategies are two complementary components of the Harmony Curriculum (Fabes et al., 2019) designed to strengthen peer processes. Both are universal, teacher-facilitated approaches that emphasize relationship-building and social integration across diverse groups of students and are predicated on Intergroup Contact Theory (Allport, 1954). Intergroup Contact Theory posits that contact and interaction with members of different social groups can contribute to intergroup outcomes, such as reduced prejudice (Pettigrew and Tropp, 2006). Positive effects of intergroup contacts, according to this theory, rely on four key conditions: equal group status, common goals, intergroup cooperation, and the support of authorities (Pettigrew, 1998). The implementation of MUBU incorporates these four core elements. Specifically, Meet Up promotes classroom-level inclusion through regular, teacher-led discussions in which students reflect on shared experiences, establish group norms, and engage in collective problem-solving. These activities aim to cultivate a cohesive classroom community and reduce subgroup boundaries, such as those based on gender, race, or social status, that can contribute to peer hierarchies and aggression (Fabes et al., 2019).

Buddy Up complements this approach by providing weekly opportunities for students to collaborate in dyads or small groups with different classmates. Through rotating partnerships, children interact with a broader range of peers, promoting familiarity and reducing biases that often underlie exclusion or aggression. By providing repeated opportunities for positive dyadic interactions with diverse classmates, Buddy Up is designed to facilitate the development of positive peer relationships and friendships, which are associated with lower levels of aggression and victimization (Hodges et al., 1997, 1999; Hong and Espelage, 2012; Salmivalli, 2010). Evidence for Buddy Up is emerging from early childhood settings. In a preschool trial, pairing children with diverse “buddies” led to more cross-gender friendships, improved interaction quality over time, increased prosocial behavior, and reduced aggression (Hanish et al., 2021, 2023; Xiao et al., 2022).

Together, Meet Up and Buddy Up (MUBU) provide a holistic approach to improving peer relationships, targeting both classroom-wide processes and individual peer interactions. Research has shown that the combination of these strategies led to improved intergroup peer relationships. Studies found MUBU improved students' perceptions of other-gender peers, including greater acceptance and prosocial behaviors (Miller et al., 2025; Xiao et al., 2023) and led to a more positive classroom climate (Miller et al., 2025). Furthermore, these improved intergroup relationships served as the mechanisms through which overall classroom supportiveness was enhanced (Miller et al., 2025). Collectively, these findings suggest that using both Meet Up and Buddy Up together can impact dyadic- and classroom-level peer processes and, in turn, may contribute to reductions in aggression and victimization.

Current study

Although there is ample research showing that peer relationships at the dyadic and classroom/group level play important roles in shaping peer aggression and victimization, few interventions focus on intervening at multiple levels. We contend that intentionally fostering interactions with diverse peers and promoting a positive classroom climate can reduce aggression and victimization. In the present study, we tested the efficacy of two classroom-based strategies, Meet Up and Buddy Up (MUBU; Xiao et al., 2023), that were jointly developed to promote students' positive interactions with diverse peers (across an array of characteristics, including gender and race/ethnicity) at both the classroom(via Meet Up) and dyadic/small group (via Buddy Up) levels, in reducing aggression and peer victimization among a sample of fourth-grade students. Based on prior research (Miller et al., 2025; Xiao et al., 2022, 2023), we hypothesized that participation in MUBU would reduce both aggression and peer victimization.

Further, we also examined whether child gender and race/ethnicity served as moderators of the relationship between participation in the intervention and peer aggression and victimization. Children of different genders and racial/ethnic backgrounds have been shown to differ in aggression and victimization in various ways, such as in their form and levels (Card et al., 2008; Casper and Card, 2017; Kennedy et al., 2024; Vitoroulis and Vaillancourt, 2015). Moreover, previous studies evaluating programs targeting bullying and victimization have also found that intervention effects may vary by gender and race/ethnicity (Kärnä et al., 2013; Kennedy, 2020; Limber et al., 2018; Salmivalli, 2001). However, evidence of such variation has been inconsistent across studies, with some reporting no significant difference by gender or race/ethnicity (Axford et al., 2020; Olweus et al., 2019; Palladino et al., 2016). Additionally, compared with the number of studies examining gender differences in intervention effects, substantially fewer studies have investigated racial/ethnic differences (Eldred et al., 2026). Therefore, we included gender and race/ethnicity as moderators of its intervention effects. Given that MUBU aims to promote positive interactions across diverse peer groups, we predicted that the intervention's effects on aggression and victimization would be stronger for boys, who typically exhibit higher levels of aggression (Card et al., 2008), and for students from racially and ethnically marginalized backgrounds, who often face higher rates of victimization (Graham, 2006).

Methods

Participants

The sample was derived from a randomized controlled trial of MUBU in four public elementary schools in the Southwestern United States (Miller et al., 2025; Xiao et al., 2023). Schools were randomized to a condition (intervention vs. control), and 4th-grade classrooms were recruited into the study. Participants were teachers and 4th graders recruited from fifteen classrooms (class size: M = 23.07, SD = 3.79, range = 15 to 30). The analytic sample comprised 15 teachers and 346 fourth-grade students who completed pretest measures.

Teachers were mostly female (80%; n = 12) and ranged in age from 25–54, with most between 45 and 54 years old (46.2%, n = 7), and were either non-Hispanic White (86.7%, n = 13) or Latino/Hispanic (13.3%, n=2). Teachers reported teaching an average of 13.93 years (SD = 5.60) and having a master's degree (66.7%, n = 10), a bachelor's degree (26.7%, n = 4), or missing education data (6.7%, n = 1).

Students' demographic information was provided by the school and primary caregivers. Primary caregivers identified as mothers/step-mothers (76.6%, n = 216), fathers/step-fathers (10.3%, n = 29), a grandmother (0.3%, n = 1), and the rest were missing (28.9%, n = 100). Student participants were on average, 9.40 years old (SD = 0.40, range: 8–10.25), with 53.5% female (n = 185) and 46.5% male (n = 161). Students were non-Hispanic, White (55.2%; n = 191), Bi-/Multi-racial (12.7%; n = 44), Latino/Hispanic (10.1%, n = 35), Asian (2.0%, n = 7), Black/African American (1.7%, n = 6), Native American (0.3%, n = 1), or race/ethnicity was missing (17.9%, n = 62) and most (70.2%, n = 243) lived in two-parent households. Caregivers were mostly married (58.4%, n = 202), separated or divorced (12.1%, n = 42), single (9.0%, n = 3), or had missing marital status (20.5%, n = 71). Over a third reported the highest level of education considering both parents as having a college degree (31.9%, n = 110), followed by some college/associates degree (22.8%, n = 79), advanced degree (22.8%, n = 68), a high school degree (GED) or less (6.6%, n = 23), and the rest were missing educational level (19.1%, n = 66). Families in our sample had a median household income of $80,000–$89,999 (range = less than $20,000 to more than $100,000).

Twelve children did not return for their post-test assessment (e.g., moved to a different school). Most of them (58.3%, n = 7%) were from the intervention group. Students who did the post-test and those who did not differed demographically on gender, race/ethnicity, highest parental education, or household type, or on aggression and peer victimization at pretest. There was a significant difference in household income, t(266) = 2.52, p = 0.01, with students who did not complete post-test having a lower mean household income of $50,000–$59,999 (M = 5.13, SD = 2.42) than completers whose mean income was about $70,000–$79,999 (M = 7.46, SD = 2.59).

Procedure

All study procedures were approved by the study institution's institutional review board and the participating school district, principals, and teachers. Four schools with 15 4th-grade classrooms were recruited from a public school district in the Southwestern United States. All teachers consented to participate in the study, and students were recruited from their grade classrooms. Consent forms were sent home with students on the first day of school. Parents provided parental permission for their child to participate, and students assented to participate. As part of the consent process, parents completed a demographic questionnaire to provide information about the participating children and families. Parents did not receive compensation for their participation. Only students who had parental permission and assented to participate were included in the study. The consent rate for intervention classrooms was 80%, and for control classrooms was 73%.

A randomized controlled trial (RCT) pre-post design was employed. Prior to the implementation of the Meet Up Buddy Up (MUBU) intervention, teachers and students completed pretest surveys at the beginning of the fall semester (August/September). Student data were collected using paper-and-pencil surveys, which took approximately 60 min to complete. The student survey consisted of an assessment battery of validated measures that assessed multiple aspects of children's school and peer experiences. The survey included self-report measures of school adjustment, peer relationships, social-cognitive processes, and social-emotional functioning, as well as peer-report measures of children's peer relationships and classroom social behaviors. A snack break was provided at the midpoint of the survey. The surveys were read aloud by one project staff member, and the class was instructed to follow along while an additional 1–2 staff members walked around the room to assist students as needed. Students received small gifts for their participation. The timing of data collection was consistent across conditions. Teachers received $100 for completing the pretest. Following the pretest assessment, teachers in control schools (six classrooms; 37.6% of students) continued business as usual, whereas teachers in intervention schools (nine classrooms; 62.4% of students) implemented MUBU with students.

Prior to the implementation of MUBU, teachers attended two training sessions in the summer (1.5 h in May; 2 h in July) on how to implement MUBU. The MUBU intervention was conducted from late August through the end of February. The intervention was composed of two parts: Meet Up and Buddy Up. Meet Up was implemented at the classroom level. Under teachers' guidance and support, students collaboratively set up classroom norms and expectations for peer interactions during the first 2 weeks of the semester by discussing the importance of inclusion and generating expectations for how they wanted to interact with one another (e.g., “we should help each other” and “we should listen to each other”; Fabes et al., 2019). Students then gathered daily at a designated time to reflect on their interactions with classmates, practice respectful listening, and review their progress toward the classroom expectations established at the beginning of the semester. Buddy Up, instead, was implemented at the dyadic level. Teachers paired students as buddies, and each pair collaborated on various activities throughout the week (e.g., reading together, completing classroom assignments, solving problems together, and going to lunch together). Buddy assignments were rotated every week to maximize opportunities for students to interact with a diverse range of peers. Teachers were encouraged to prioritize pairing students with diverse classmates, including other-gender peers, when feasible, while maintaining flexibility to accommodate classroom composition and instructional needs. Both Meet Up and Buddy Up were designed to enhance each student's social experiences and foster positive peer relationships within the classroom. Intervention fidelity was monitored throughout implementation using teacher implementation logs, classroom observations, and teacher and student reports assessing implementation exposure, adherence, quality, and responsiveness. Both teachers and students demonstrated high levels of implementation fidelity to the MUBU program (see Xiao et al., 2023, for a detailed description of the fidelity procedures and results).

Following the intervention, post-test data were collected during the spring semester (February/March). Teachers and students completed the same set of surveys as administered at pretest. Teachers received $100 for completing posttest measures, and students received small gifts for their participation. The intervention teachers received an additional $200 for attending training sessions, implementing the intervention, and completing process measures ($50 for training sessions and $150 for implementation and process measures).

Measures

The current study relied on teacher reports of children's aggression and victimization and demographic information provided by schools and parents.

Aggression

The 7-item aggression subscale from the teacher-report Child Behavior Scale (CBS) Ladd and Profilet, 1996) assessed children's physical and verbal aggressive behavior. Teachers rated items (e.g., this child is a student who fights) on a 3-point Likert scale (0 = “Doesn't apply,” 1 = “Applies sometimes,” 2 = “Certainly applies”). All items were averaged to create a total score with higher scores representing higher levels of aggression. The measure demonstrated excellent reliability at both T1 (α = 0.91) and T2 (α = 0.95).

Victimization

The 5-item teacher-report Peer Victimization Scale (Ladd and Kochenderfer-Ladd, 2002) assessed the frequency with which children experienced victimization from peers in the previous 2 weeks. Teachers rated items (i.e., How often is this child hit or kicked by other children?) on a 5-point Likert scale (0 = Never to 4 = Everyday). All items were averaged to create a total score with higher scores representing higher levels of peer victimization. The measure demonstrated good reliability at both T1 (α = 0.86) and T2 (α = 0.93).

Demographics

Schools and parents reported demographic information. Schools reported child gender. Parents reported their relationship to the participating child, the race/ethnicity of both parents, their marital status, annual family income, education level of both parents, occupation of both parents, household type, and their child's age and race/ethnicity.

Child gender (0 = female, 1 = male), child age (in years), child race/ethnicity (0 = White, 1 = Racial/ethnically minoritized), household type (0 = two parent household, 1 = single parent household), annual household income (1 = under $20,000 – 10 = over $100,000), and parental education level which was calculated taking the highest education of both parents (1 = high school graduate or less, 2 = Some College/Associates Degree, 3=College Degree, 4=Advanced Degree) were considered as covariates.

Data analysis plan

Descriptive analyses were conducted, and potential covariates were examined through bivariate correlations. Covariates that showed significant associations with aggression or victimization were included in subsequent analyses. Preliminary analyses were conducted to examine baseline differences between the control and intervention groups on demographic characteristics and differences in aggression and victimization by intervention condition, gender, and race/ethnicity at both pretest and posttest. Because children were nested within classrooms, intraclass correlation (ICC) analyses were examined for aggression and victimization to determine the proportion of variance at the between-classroom level. These analyses were completed in SPSS 29.0.

To examine whether there were differences in teacher-reported aggression and victimization before and after the intervention, a two-wave Latent Change Score model (2W-LCS) Henk and Castro-Schilo, 2016), which offers a less biased alternative to traditional difference-score approaches, was estimated. In this model, latent change scores for aggression and victimization served as the outcome variables. For the first research question, the effects of the intervention on changes in aggression and victimization were examined, controlling for covariates. Specifically, the latent change scores for aggression and victimization were estimated using scale scores, which were each regressed on intervention conditions (0 = control group; 1 = intervention group) and the covariates. The latent change scores of aggression and victimization were also allowed to covary. To address the second research question, gender and race/ethnicity were examined as moderators in separate models. The first model included a gender*latent change score interaction to test whether the intervention effects on aggression and victimization differed between males and females. The second model included a child race/ethnicity*latent change score interaction to test whether the intervention effects on aggression and victimization differed between White and racial/ethnically minoritized students. Significant interactions were probed with simple slope analysis. See Figure 1 for models.

Conceptual Model. The figure shows the estimated model for the moderation analysis. Covariances are not displayed. Condition: 0 = control, 1 = MUBU intervention. Gender: 0 = female, 1 = male; Race/ethnicity: 0 = White, 1 = Racial/ethnically minoritized.
Figure 1. Conceptual Model. The figure shows the estimated model for the moderation analysis. Covariances are not displayed. Condition: 0 = control, 1 = MUBU intervention. Gender: 0 = female, 1 = male; Race/ethnicity: 0 = White, 1 = Racial/ethnically minoritized.

Given interest in student level outcomes and the small number of classrooms, Bayesian Markov Chain Monte Carlo (MCMC) estimation approach (McNeish and Stapleton, 2016; Xiao et al., 2023) was employed to account the nested data due to classroom-level clustering and the non-normality in the outcome variables (T1 & T2 aggression: skewness = 4.40 and 3.71; kurtosis = 21.86 and 14.3, respectively) and victimization (T1 & T2 victimization: skewness = 4.64 and 4.11; kurtosis = 25.75 and 19.02, respectively). This is a recommended approach based on prior simulation research on small level 2 sample sizes with clustered data (McNeish and Stapleton, 2016). All regression coefficients were assigned normal prior distributions, N (0, 1000). The variances of the outcome variables (i.e., latent change scores for aggression and victimization) were assigned inverse-gamma priors, IG(0.01, 0.01), and the prior distributions for covariances followed Mplus defaults (Muthén and Muthén, 1998-2017). Three chains were run with 20,000 iterations for each, and posterior means were used as point estimates. The 95% confidence interval (CI) was estimated and was statistically significant when the intervals did not include zero. These analyses were completed in Mplus 8.11.

Results

Preliminary analysis

Descriptive statistics and correlations for all study variables are presented in Table 1. Gender, race/ethnicity, parental highest level of education, and household income were significantly or marginally correlated with either aggression and victimization at T1 or T2 and were therefore included as covariates. Household type was also correlated with aggression, but was not included as a covariate because it was moderately correlated with household income (r = −0.49 Cohen, 1992). Independent samples t-tests indicated no significant baseline differences between the intervention and control groups on demographic characteristics (Table 2).

Table 1. Descriptive statistics and bivariate correlations of demographics characteristics and study variables.

Variables12345678910
1. Age——————————
2. Gender (1 = male)0.27***—————————
3. Race/ethnicity (1 = minoritized)0.060.01————————
4. Parental highest education level0.050.04-.0.16**———————
5. Household type (1 = single parent)−0.05−0.080.05−0.15*——————
6. Household income−0.010.02−0.18**0.40***−0.49***—————
7. Aggression (T1)0.080.13*−0.01−0.070.16**-.0.17**————
8. Aggression (T2)0.060.030.11+−0.090.10−0.26***0.32***———
9. Victimization (T1)0.030.14*−0.04−0.13*0.06−0.100.45***0.26***——
10. Victimization (T2)0.100.12*0.04−0.17**0.00−0.110.24***0.44***0.65***—
N282346284280279268329331328330
Mean9.400.470.332.800.137.390.090.130.100.15
SD0.400.500.470.900.342.610.270.370.300.45

+ p < 0.10, *p < 0.05, **p < 0.01, ***p < 0.001.

Table 2. Bassline demographic characteristics by intervention group.

Control (n = 130)Intervention (n = 216)Total (n = 346)tdfp
VariablesM(SD)M(SD)M(SD)
Age9.44 (0.38)9.39 (0.41)9.40 (0.40)1.002800.32
Gender (% male)0.45 (0.50)0.48 (0.50)0.47 (0.50)−0.553440.58
Race/ethnicity (% racial/ethnicity minority)0.31 (0.46)0.34 (0.48)0.33 (0.47)−0.562820.58
Household type (% single parent)0.12 (0.33)0.13 (0.34)0.13 (0.34)−0.192770.85
Income7.33 (2.63)7.43 (2.60)7.39 (2.61)−0.302660.77
Highest parental educational level2.70 (0.95)2.85 (0.87)2.80 (0.90)−1.292780.20

T1, pretest; T2, posttest.

Descriptive statistics for aggression and victimization at T1 and T2 by intervention condition, gender, and race/ethnicity are shown in Table 3. Independent samples t-tests indicated that children in the control group had significantly higher levels of aggression than children in the intervention group at both T1 (t(327) = 3.16, p < 0.01) and T2 (t(329) = 5.17, p < 0.001). Similarly, children in the control group had significantly higher levels of victimization than children in the intervention group at T1, t(326) = 4.46, p < 0.001, and T2, t(328) = 5.98, p < 0.001. Gender differences were also found. Gender differences were also observed. Boys demonstrated higher levels of aggression than girls at T1, t(327) = −2.31, p = 0.02, but not at T2, t(329) = −0.48, p = 0.63. Boys also experienced higher levels of victimization than girls at both T1, t(326) = −2.55, p = 0.01, and T2, t(328) = −2.27, p = 0.02. No significant differences in aggression or victimization were observed by race/ethnicity at either T1 (aggression: t(279) = 0.11, p = 0.92; victimization: t(278) = 0.69, p = 0.49) or T2 (aggression: t(271) = −1.87, p = 0.06; victimization: t(271) = −0.74, p = 0.46).

Table 3. Study variables by intervention group, gender, and race/ethnicity.

ControlInterventiontdfp
VariablesNM(SD)NM(SD)
Aggression (T1)1160.15 (0.34)2130.06 (0.22)3.16327< .01
Aggression (T2)1230.26 (0.53)2080.05 (0.18)5.17329< .001
Victimization (T1)1160.19 (0.45)2120.04 (0.14)4.46326< .001
Victimization (T2)1220.33 (0.66)2080.04 (0.17)5.98328< .001
GirlsBoys*t**df**p*
*N**M*(*SD*)*N**M*(*SD*)
Aggression (T1)1750.06 (0.23)1540.13 (0.31)−2.313270.02
Aggression (T2)1790.12 (0.39)1520.14 (0.34)−0.483290.63
Victimization (T1)1750.06 (0.23)1530.14 (0.36)−2.553260.01
Victimization (T2)1790.09 (0.37)1510.21 (0.52)−2.273280.02
WhiteMinoritized*t**df**p*
N*M*(*SD*)*N**M*(*SD*)
Aggression (T1)1880.09 (0.28)930.06 (0.22)0.112790.92
Aggression (T2)1840.11 (0.34)900.05 (0.18)−1.872720.06
Victimization (T1)1870.10 (0.31)930.04 (0.14)0.692780.49
Victimization (T2)1840.14 (0.47)890.04 (0.17)−0.742710.46

T1, pretest; T2, posttest.

Intraclass correlations (ICCs) indicated meaningful classroom-level clustering (ICC > 0.10) for T1 victimization (ICC = 0.15), T2 aggression (ICC = 0.33), and T2 victimization (ICC = 0.36), supporting the need to account for nesting in the primary analyses.

Intervention effects

To understand change over time in our constructs, an unconditional 2W-LCSM was estimated for aggression and victimization in a single model; results are presented in Table 4 (see Model 1). Change over time in aggression and victimization was significant. There were significant increases in both aggression (β = 0.36, [0.002, 0.36], latent change T1: M = 0.09, SE = 0.02, T2: M = 0.13, SE = 0.04) and victimization over time (β = 0.21, [0.05, 0.40]; T1: M = 0.10, SE = 0.02; T2: M = 0.15, SE = 0.04). Next, the direct effects of the MUBU intervention on change in aggression and victimization were evaluated, controlling for covariates. Results support our first hypothesis. The MUBU intervention was significantly negatively associated with change in both aggression (β = −0.23, [−0.44, −0.06]) and victimization (β = −0.25, [−0.43, −0.09]). Compared to children in the control group, children who received the MUBU intervention experienced significantly smaller increases in both aggression and victimization over time. Specifically, the estimated mean increase in aggression was 0.08 (SE = 0.04) for the intervention group compared with 0.20 (SE = 0.09) for the control group. Similarly, the estimated mean increase in victimization was 0.09 (SE = 0.04) for the intervention group compared with 0.21 for the control group.

Table 4. Standardized Effects and 95% Confidence Intervals.

AggressionVictimization
VariablesβPosterior SD95% CIβPosterior SD95% CI
Model 1: unconditional model
Latent change scores0.160.06[0.002, 0.36]0.210.09[0.05, 0.40]
Model 2: intervention effects
Condition−0.230.09[–0.44, –0.06]−0.250.09[–0.43, –0.09]
Gender−0.070.09[−0.26, 0.09]0.100.08[−0.05, 0.27]
Race/ethnicity0.150.10[−0.02, 0.36]0.130.09[−0.04, 0.30]
Parental education0.060.10[−0.14, 0.27]−0.150.10[−0.35, 0.03]
Income−0.190.11[−0.43, 0.01]−0.020.10[−0.22, 0.16]
Model 3: moderation by gender
Condition−0.240.12[–0.50, –0.01]−0.170.11[−0.40, 0.04]
Gender−0.070.14[−0.36, 0.20]0.220.14[−0.03, 0.50]
Race/ethnicity0.160.10[−0.03, 0.36]0.120.09[−0.05, 0.31]
Parental education0.060.10[−0.13, 0.26]−0.160.10[−0.36, 0.03]
Income−0.190.11[−0.42, 0.01]−0.020.10[−0.22, 0.17]
Condition* gender0.000.16[−0.32, 0.33]−0.180.15[−0.49, 0.12]
Model 4: moderation by race/ethnicity
Condition−0.010.10[−0.21, 0.19]−0.110.10[−0.31, 0.07]
Gender−0.090.09[−0.28, 0.08]0.090.08[−0.06, 0.27]
Race/Ethnicity0.610.17[0.30, 0.97]0.410.16[0.13, 0.76]
Parental education0.040.10[−0.15, 0.23]−0.170.11[−0.42, 0.01]
Income−0.160.10[−0.36, 0.03]0.000.10[−0.20, 0.19]
Condition * race/ethnicity−0.610.18[–0.99, –0.27]−0.380.17[–0.76, –0.08]

N = 346. Numbers in bold represent p < 0.05. Condition: 0 = control, 1 = MUBU intervention.

Gender: 0 = female, 1 = male; Race/ethnicity: 0 = White, 1 = Racial/Ethnically Minoritized. CI, confidence internal.

Moderation of gender and race/ethnicity on intervention effects

Gender and race/ethnicity were examined as moderators of intervention effects on change in aggression and victimization; results are presented in Table 4 (see Models 3 and 4). Gender moderation results did not support our second hypothesis. Gender did not moderate the effects of the intervention on changes in aggression (β = 0.00, [−0.32, 0.33]) or victimization (β = −0.18, [−0.49, 0.12]).

In support of our third hypothesis, race/ethnicity moderated intervention effects on changes in aggression and victimization. Results indicated a significant negative interaction between race/ethnicity and intervention on change in aggression (β = −0.61, [−0.99, −0.27]) and change in victimization (β = −0.38, [−0.76, −0.08]). Simple slopes are presented in Figure 2.

Simple Slopes Plots for Child Race/Ethnicity Moderation. The figure shows unstandardized estimates for the simple slopes of intervention condition on change aggression **(left)** and victimization **(right)** by race/ethnicity. The demographic covariates (i.e., gender, parental education, and household income) were set as 0 to depict simple slopes.
Figure 2. Simple Slopes Plots for Child Race/Ethnicity Moderation. The figure shows unstandardized estimates for the simple slopes of intervention condition on change aggression (left) and victimization (right) by race/ethnicity. The demographic covariates (i.e., gender, parental education, and household income) were set as 0 to depict simple slopes.

For aggression, children from racially/ethnically minoritized groups who received the MUBU intervention experienced a reduction in aggression over time, whereas those in the control group experienced an increase. Specifically, the estimated mean change in aggression was −0.02 for students in the intervention group and 0.34 for students in the control group. In contrast, among White students, there was little difference between the intervention and control groups, with both groups showing an estimated mean change in aggression of 0.02.

For victimization, students from racially/ethnically minoritized groups who received the MUBU intervention experienced no change in victimization over time, whereas those in the control group experienced an increase. Specifically, the estimated mean change in victimization was 0.00 for students in the intervention group, compared with 0.28 for students in the control group. In contrast, among White students, there was little difference between the intervention and control groups, with estimated mean changes in victimization of 0.01 and 0.07 for the intervention and control groups, respectively.

Discussion

Peer relationships in school play a crucial role in the development, elaboration, and maintenance of aggressive behaviors and victimization (Hodges et al., 1997; Salmivalli, 2010). To date, most approaches to the prevention of peer aggression have adopted an individual focus, largely through social-emotional learning or cognitive-behavioral frameworks, which have produced only negligible to small improvements in peer relationships or social acceptance (De Mooij et al., 2020; Ttofi and Farrington, 2011). This suggests that traditional, individually targeted didactic approaches may not trickle up to the friendship and peer network dimensions underlying peer aggression (Espelage, 2014; Salmivalli et al., 2010). Conversely, relationally focused interventions, particularly those predicated on promoting intergroup contact, offer an approach that could change peer relational processes associated with aggression and victimization (Fabes et al., 2019; Pollak et al., 2023).

Meet Up and Buddy Up were jointly developed to promote students' positive interactions with diverse peers (across an array of characteristics, including gender and race/ethnicity) at both the classroom (via Meet Up) and dyadic/small group (via Buddy Up) levels. Targeting the nested nature of peer relations is important, as developmental and network scholars have recognized both as contributors to peer aggression (Mouttapa et al., 2004; Rubin et al., 2015). Prior studies have shown that the combination of these strategies led to improved intergroup peer relationships. Specifically, studies found that MUBU improved students' perceptions of other-gender peers, including greater acceptance and prosocial behaviors (Miller et al., 2025; Xiao et al., 2023), and led to a more positive classroom climate (Miller et al., 2025). The primary purpose of the current study was to build upon this work by assessing impacts on peer aggression and victimization. Furthermore, given that MUBU focuses on promoting diverse intergroup contact, we examined child gender and race/ethnicity as a moderator of the relationship between participation in the intervention and peer aggression and victimization.

Children in the MUBU classrooms demonstrated a less pronounced increase in both aggression and victimization relative to their peers in the control group one semester later. Although an increase in these behaviors was observed across groups, reflecting typical developmental patterns (Williford et al., 2011), the program attenuated the typical developmental escalation of these behaviors. Although the study did not directly test underlying mechanisms, the results are consistent with theoretical and empirical work highlighting the role of peer relationships and classroom social dynamics in shaping aggression and victimization (Espelage et al., 2014; Hodges et al., 1997; Mouttapa et al., 2004; Rubin et al., 2015). The attenuated growth observed among MUBU participants suggests that interventions promoting structured, inclusive interactions may influence the social contexts in which aggression and victimization emerge, potentially reducing risk even without eliminating these behaviors. This pattern is consistent with prior research showing that interventions targeting peer relationships and social-emotional competencies can reduce the likelihood or intensity of aggressive behaviors and victimization experiences over time (Durlak et al., 2011; Pollak et al., 2023; Ttofi and Farrington, 2011). Additionally, these findings extend prior evidence that MUBU improves classroom climate and prosocial engagement (Miller et al., 2025; Xiao et al., 2023), demonstrating that such relational improvements may translate into observable behavioral benefits. Overall, the results underscore the value of multi-level, school-based interventions in moderating developmental trajectories of aggression and victimization, highlighting the potential of approaches that address both peer networks and classroom norms.

Findings suggest that although the main effects on aggression and victimization were significant, there were significant differences by race/ethnicity. Mainly, effects for aggression were stronger for racial/ethnically minoritized students, such that they showed a small decrease in aggression over time, while White students showed a small increase. For victimization, racial/ethnically minoritized students in the MUBU intervention showed greater benefit, indicated by mitigation of increases in victimization, when compared to racial/ethnically minoritized students in the control group. No significant differences emerged for White students. However, contrary to hypotheses, the strength of findings did not differ for males and females. Taken together, moderation analyses imply that both the strength and direction of effects of intervention on aggression and victimization vary on the basis of race/ethnicity.

In schools with a majority White/Caucasian student population, students from racially/ethnically minoritized groups may be more likely to experience social marginalization, including isolation or exclusion, and peer relationships often form within racially homogeneous groups (Graham, 2006; Killen et al., 2013). Such racial segregation in peer networks is associated not only with a higher risk of peer victimization but also with diminished opportunities for supportive relationships (Graham et al., 2014). Interventions like MUBU that emphasize cooperative group work and structured peer activities can expand students' opportunities for meaningful contact across racial/ethnic boundaries, increasing the likelihood of positive peer interactions beyond existing social cliques. Empirical evidence suggests that cross-racial/ethnic friendships are uniquely predictive of decreases in peer victimization and increases in peer support, particularly in diverse classroom settings (Kawabata and Crick, 2011). Moreover, cross-ethnic friendships have been linked to lower levels of peer rejection and internalizing symptoms over time, indicating broader benefits for social adjustment that extend beyond immediate peer dynamics (Kawabata and Crick, 2015). Research on cross-group peer relations further suggests that children with diverse friendship ties are perceived as more socially competent and connected, which is theorized to reduce tendencies toward exclusionary or aggressive behaviors by fostering inclusive norms and reducing social anxiety around out-group peers (Graham et al., 2014; Killen et al., 2013). MUBU provides structured opportunities for positive interactions with diverse peers and has been shown to improve intergroup peer relationships and classroom climate (Miller et al., 2025; Xiao et al., 2023), processes that may foster more inclusive peer relationships and greater classroom social integration. These changes may be particularly beneficial for students from racially/ethnically minoritized groups, providing one potential explanation for the stronger intervention effects observed in the present study. However, because the present study did not directly assess students' experiences of social marginalization, friendship formation, or changes in peer relationships, future research examining these processes would help clarify the mechanisms underlying the observed moderation effects.

Strengths, Limitations, and Future Directions

The current study has notable strengths. First, the use of an RCT design allows for more rigorous testing of the intervention's causal effects on outcomes. Second, Bayesian estimation allowed us to account for the non-normal distribution of the outcomes and the clustering of students, given the small level-2 sample size (McNeish and Stapleton, 2016). Third, this study extends previous MUBU research by examining aggression and victimization, broadening the understanding of the potential benefits of relationship-focused interventions. Finally, by examining moderation by gender and race/ethnicity, the study provides insight into for whom the intervention may be most effective.

As with all research, this study has limitations that warrant consideration. First, teachers reported on students' aggression and victimization experiences, which may not be concordant with self-reported victimization, particularly among students experiencing more frequent victimization or among females (Ladd and Kochenderfer-Ladd, 2002; Løhre et al., 2011). Teacher reports of victimization remain rare, and face threats to validity due to restricted knowledge of incidents that occur outside their awareness, or observation, which may explain why teachers generally show less concordance with females (who tend to engage in proportionately more indirect verbal and relational aggression) than males, who may proportionately engage in more overt physical and verbal aggression (see Ladd and Kochenderfer-Ladd, 2002). Despite the caution regarding limited knowledge, biases, or halo effects, teachers can provide a more fine-tuned and nuanced understanding of aggression than younger informants would. During middle childhood, multiple informants may generate the most comprehensive assessment, maximizing non-shared information (Ladd and Kochenderfer-Ladd, 2002). Future research would benefit from incorporating multiple informants, including student self-reports, to provide a more comprehensive assessment of aggression and victimization.

Second, this study drew upon a smaller sample and, as such, dichotomized race/ethnicity, thereby losing potentially important differences among diverse racial/ethnic groups. The uneven sample sizes between the intervention and the control groups should also be acknowledged. The relatively smaller control group may have increased the uncertainty of the estimated intervention effects. Findings should be replicated on a larger, racially diverse sample with more balanced sample sizes across conditions.

Third, because this study evaluated a universal intervention in a community sample, baseline levels of aggression and victimization were relatively low, which may have limited variability in these outcomes. Although lower base rates can reduce statistical power to detect intervention effects, significant intervention effects were nevertheless observed for both aggression and victimization. Future research should examine the effectiveness of MUBU across school contexts with varying levels of aggression and victimization to better understand its impact.

Finally, the present study was limited to fourth-grade students. Peer relationships, classroom social dynamics, and the nature of aggression and victimization change across development, and it is therefore unclear whether MUBU would produce similar effects in younger children or adolescents. In addition, although we proposed that improvements in peer relationships and classroom climate may help explain the stronger intervention effects observed among racially/ethnically minoritized students, these mechanisms were not directly assessed. Future research should examine these processes across a broader range of developmental periods and school settings to better understand both the generalizability of MUBU and the mechanisms through which it influences aggression and victimization.

Despite these limitations, the current RCT of MUBU provides further evidence that relationally targeted, universal classroom strategies promote climates that reduce the escalation of aggression and victimization during middle childhood. Drawing on Intergroup Contact Theory, MUBU provides simple, teacher-facilitated opportunities for students to engage in structured positive interactions with diverse peers. Importantly, the present findings build upon previous MUBU and Buddy Up research, as well as related relational approaches (e.g., cooperative learning), bolstering empirical support for these approaches in fostering inclusive classroom environments that buffer against aggression and victimization. Together, these findings highlight the promise of relationship-centered interventions for promoting positive peer experiences and reducing aggression and victimization in elementary school classrooms.

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Footnotes

Edited by: Piotr P. Brud, Cardinal Stefan Wyszyński University, Poland

Reviewed by: Monika Krah, Georgia Southern University, United States

Mun Wong, The Education University of Hong Kong, Hong Kong SAR, China

Statements

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The author RF declared that they were an editorial board member of Frontiers at the time of submission. This had no impact on the peer review process and the final decision.

Funding

The author(s) declared that financial support was received for this work and/or its publication. The research reported here was supported by the T. Denny Sanford Foundation and the T. Denny Sanford School of Social and Family Dynamics, Arizona State University.

Data availability

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics approval

The studies involving humans were approved by Arizona State University Institutional Review Board. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation in this study was provided by the participants' legal guardians/next of kin.

Author contributions

AM: Conceptualization, Formal analysis, Writing – original draft, Writing – review & editing. HR: Conceptualization, Data curation, Formal analysis, Writing – review & editing, Writing – original draft. SL: Conceptualization, Investigation, Writing – original draft, Writing – review & editing. LH: Conceptualization, Funding acquisition, Investigation, Methodology, Writing – review & editing. RF: Conceptualization, Funding acquisition, Investigation, Methodology, Writing – review & editing. CaM: Conceptualization, Funding acquisition, Investigation, Methodology, Writing – review & editing. CFM: Conceptualization, Investigation, Writing – review & editing. LW: Conceptualization, Investigation, Methodology, Writing – review & editing.

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Citation

McDonald, A. R., et al. (2026). Reducing aggression and peer victimization in elementary classrooms: efficacy of the meet up and buddy up interventions. Frontiers in Developmental Psychology, Volume 4. https://doi.org/
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4 - 2026

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Copyright © 2026 McDonald, Ren, Low, Hanish, Fabes, Martin, Miller and Wheeler.

License: https://creativecommons.org/licenses/by/4.0/

*Correspondence: Sabina Low

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