Background <p>Bullying in schools is widespread and can lead to severe short- and long-term physical and psychological burden for those affected.</p> Objective <p>This systematic review summarizes the evidence on the effectiveness of school-based, theory-driven prevention and intervention programs against bullying and evaluates their efficacy in preventing and reducing aggressive behavior.</p> Methods <p>We searched FIS-Bildung and PsycInfo for German- and English-language publications from 1980 to August 2024. Included were only theory-driven programs implemented by teachers in regular classroom settings that target physical, verbal, relational, and cyberbullying and measure bullying via self- or peer-reports. Of 892 records, six systematic reviews and meta-analyses met the inclusion criteria.</p> Results <p>All six reviews report statistically significant but predominantly small to moderate effects of school-based measures. Holistic, whole-school approaches in particular yield reductions in bullying.</p> Discussion <p>The modest effect sizes suggest that current programs require optimization in dosage, duration, and implementation. Moreover, standardized evaluation designs and longitudinal efficacy data are lacking.</p> Conclusion <p>School-based anti-bullying programs currently demonstrate limited effectiveness. Future efforts should employ multimodal, theory-driven approaches with clearly defined moderators, process and outcome evaluations, and targeted teacher training to achieve sustainable effects.</p>