Identifying factors that influence peer aggression and victimization is important because of their high prevalence rates and associated negative outcomes during early adolescence. Limited research has examined the impact of environmental and contextual factors, such as school climate, on peer aggression and victimization. This study longitudinally examined bidirectional relations between school climate and peer aggression and between school climate and victimization over 6 months. Participants were 265 sixth-, seventh-, and eighth-grade students (50% female; 82% African American). Bidirectional path regression analyses showed that students who reported higher levels of positive student-teacher relationships at Time 1 engaged in lower frequencies of aggression and experienced less victimization at Time 2. Students who reported higher levels of awareness and reporting of violence at Time 1 had more positive student-teacher relationships and engaged in lower frequencies of aggression at Time 2.