Predicting change in children's aggression and victimization using classroom-level descriptive norms of aggression and pro-social behavior.

This study examined aggressive and pro-social classroom descriptive norms as predictors of change in aggression and victimization during middle childhood. Participants included 948 children in third through fifth grade. Measures of teacher-reported aggressive and peer-reported pro-social descriptive norms were completed at the onset of the study. Children completed self-report measures of aggression and victimization on three occasions during one academic year. Multilevel growth models were analyzed to determine the amount of student-reported change in aggression and victimization attributable to the classroom norm variables. Results indicated that students in classrooms with higher initial mean levels of aggression reported larger increases in aggression and victimization over the school year. In contrast, boys with higher initial levels of aggression reported smaller increases in aggression than boys with lower initial levels of aggression, and both boys and girls with higher initial aggression reported declining victimization over the school year. Pro-social classroom norms were unrelated to change in aggression and victimization. The implications of the findings for future studies on the influence of classroom social norms as well as interventions for aggression and victimization are discussed.