Effectiveness of school-based programs to reduce bullying: a systematic and meta-analytic review

This article presents a systematic review and meta-analysis of the effectiveness of anti-bullying programs in schools. Studies were included if they evaluated the effects of an anti-bullying program by comparing an intervention group who received the program with a control group who did not. Four types of research design were included: a) randomized experiments, b) intervention-control comparisons with before-and-after measures of bullying, c) other intervention-control comparisons, and d) age-cohort designs. Both published and unpublished reports were included. All volumes of 35 journals from 1983 up to the end of May 2009 were hand-searched, as were 18 electronic databases. Reports in languages other than English were also included. A total of 622 reports concerned with bullying prevention were found, and 89 of these reports (describing 53 different program evaluations) were included in our review. Of the 53 different program evaluations, 44 provided data that permitted the calculation of an effect size for bullying or victimization. The meta-analysis of these 44 evaluations showed that, overall, school-based anti-bullying programs are effective: on average, bullying decreased by 20–23% and victimization decreased by 17–20%. Program elements and intervention components that were associated with a decrease in bullying and victimization were identified, based on feedback from researchers about the coding of 40 out of 44 programs. More intensive programs were more effective, as were programs including parent meetings, firm disciplinary methods, and improved playground supervision. Work with peers was associated with an increase in victimization. It is concluded that the time is ripe to mount a new program of research on the effectiveness of anti-bullying programs based on these findings.