The goal of this study was to examine behavioral norm effects in 2 peer contexts (classroom, school) on adolescent substance use (tobacco, alcohol, cannabis) and aggressive behaviors (bullying, physical fighting). Participants were 5,642 adolescents (Mage 5 14.29 years, SD 5 1.26; 49% boys). There were 3 hypotheses. First, behavioral norms in both contexts affect individual behavior. Second, classroom norms have stronger effects on individual behavior than school norms. Third, classroom and school norms interact and exacerbate each other’s influence. Results indicated that classroom norms had stronger effects than school norms on individual tobacco and alcohol use. Furthermore, school norms had equal or stronger effects than classroom norms on the 2 indicators of aggressive behaviors. There was no evidence for an interaction between classroom and school norms for any dependent variable. This study demonstrates that the complexity of multiple (nested) peer contexts should be considered to fully understand peer influence processes.