This study examined relationships between teacher implementation of a comprehensive bullying prevention program and student outcomes. Implementation in third- through sixth-grade classrooms (N = 36) was measured by observation and teacher report. Student outcomes were measured by student surveys and teacher ratings of peer social skills (N = 549) and observations of playground behaviors (n = 298). Multilevel modeling showed that teacher coaching of students involved in bullying was associated with less observed victimization and destructive bystander behavior among students engaged in these problems at pretest, and less observed aggression among fifth- and sixth-grade students. Support for skill generalization related to reductions in observed aggression and victimization among older students. Adherence to lessons was associated with higher ratings of peer social skills. Quality of lesson instruction corresponded to greater self-reported victimization, as well as more perceived difficulty responding assertively to bullying. Implications for school-based practice and future research directions are discussed. (Contains 7 tables and 2 footnotes.)