BACKGROUND: Teacher's exposure to pupils' aggressive behaviour is an international phenomenon that requires more attention. This study examined if organizational prevention measures are associated with decreased risk of pupils' aggressive behaviour. METHOD: 94 public schools in Denmark participated. Questionnaire data about preventive measures at school level were collected in 2018 and outcome data about pupils' aggressive behaviour in form of harassment, threats and violence towards teachers were collected in 2019. In total, 1198 teachers participated in both rounds. The analyses were performed using multivariate logistic regressions with cluster adjusted standard errors to account for cluster effects. RESULTS: The results were mixed. Violence prevention climate perceptions at the management level decreased the risk of pupils' aggressive behaviour, however when adjusting for baseline harassment, threats, and violence the associations became statistically insignificant. Violence prevention climate perceptions at co-worker level statistically significant decreased the risk of pupils' aggressive behaviour in form of violence even when adjusted for baseline violence. Practice and procedures statistically significantly decreased the risk of harassment. The results for conflict management training were mixed, while supervision in case of challenging pupils decreased the risk of harassment, threats, and violence, but none of the associations were statistically significant. Finally, the registration of threats and violence statistically significantly increased the risk of threats and violence at follow-up. CONCLUSION: This study shows that implementing organizational prevention measures in public schools may reduce the risk of pupils' aggressive behaviour towards teachers. It is, therefore, recommended to implement organizational prevention measures in public schools to reduce the risk of pupils' aggressive behaviour towards teachers.