Going to scale: A nonrandomized nationwide trial of the KiVa antibullying program for grades 1–9.

OBJECTIVE: The effects of school-based antibullying programs have typically been examined on small samples, with number of schools ranging from 1 to 78 (Farrington 51% boys and 49% girls). Victims and bullies were identified with the global questions from the Revised Olweus Bully/Victim Questionnaire (Olweus, 1996), utilizing the criteria suggested by Solberg and Olweus (2003). The program effects were examined by calculating odds ratios based on a cohort-longitudinal design, correcting the standard errors for clustering. RESULTS: During the first 9 months of implementation, the KiVa program reduced both victimization and bullying, with a control/intervention group odds ratio of 1.22 (95% CI 1.19, 1.24) for victimization and 1.18 (95% CI 1.15, 1.21) for bullying. CONCLUSIONS: Generalized to the Finnish population of 500,000 students, this would mean a reduction of approximately 7,500 bullies and 12,500 victims.