This longitudinal study examined trajectories of change in adolescents' perceptions of four dimensions of school climate (academic support, behavior management, teacher social support, peer social support) and the effects of such trajectories on adolescent problem behaviors. We also tested whether school climate moderated the associations between deviant peer affiliation and adolescent problem behaviors. The 1,030 participating adolescents from 8 schools were followed from 6th through 8th grades (54% female; 76% European American). Findings indicated that all the dimensions of school climate declined and behavioral problems and deviant peer affiliation increased. Declines in each of the dimensions were associated with increases in behavioral problems. The prediction of problem behavior from peer affiliation was moderated by adolescents' perceptions of school climate.