A total of 5,025 students from 10 secondary schools finished the screening questionnaires. Among them, 622 students were classified as reactive aggressors, 266 students as proactive aggressors, 271 students as aggressive victims and 372 as pure victims.

1. Proactive Aggressor Group

The results showed a significant reduction in the students’ aggressive behaviour, attention problems, delinquent behaviour and proactive aggression after the intervention.

2. Aggressive Victim Group

The group intervention was also effective for the aggressive victims. Compared with the pre-test results, the aggressive victims’ anxiety and peer victimisation declined significantly in the post-test. Because both aggressive victims and reactive aggressors display similar aggressive behaviours, the remarkable reduction in the aggressive victims’ reactive aggression reflected their less aggressive behaviour in response to bullying. Additionally, a significant reduction was found in the students’ anger reaction and anger in, which means they became less angry when challenged and provoked and had less tendency to suppress their anger. Further, their anger control significantly improved, demonstrating that the students became better at controlling their angry feelings. In a word, the results of this study suggest that the students felt safer in school after the group intervention.