Effectiveness of School-Based Interventions for Reducing Bullying and Victimisation: A Subgroup Analysis from the BRAVE Meta-Analysis

Bullying remains a pervasive challenge in educational settings worldwide, with serious implications for students’ well-being and learning. This meta-analysis presents a focused subgroup analysis from the BRAVE-project, synthesising 93 group comparisons on bullying analysis revealed statistically significant effects for both bullying (d = 0.37) and victimisation (d = 0.17), exceeding effect sizes reported in previous meta-analyses. However, high heterogeneity (I² > 96%) highlights substantial variation between studies. Moderator analyses identified several content- and method-related factors that influence programme effectiveness. Interventions grounded in interactionist or cognitive theories, implemented in classroom settings with high implementation fidelity, were more effective than behaviourist or structurally unspecific programmes. Programmes conducted in North America showed stronger effects than those in Europe, suggesting contextual variation. Notably, randomisedcontrolled trials reported higher effect sizes than quasi-experimental designs. These findings underscore the importance of theory-driven, context-sensitive prevention strategies and the need for differentiated implementation practices. Implications for school policy and futureresearch are discussed, particularly in relation to intervention design, professional training, and international evidence gaps.