Although there has been wide dissemination of research-based psychosocial prevention programs, a similarly strong research base to guide program implementation has been lacking. Program implementation has been particularly difficult for schools, due partly to insufficient understanding of how school ecologies interact with these programs. This study examined the effects of multiple dimensions of school climate on level and rate of change in implementation of a violence prevention intervention across three school years. Using multi-level modeling, the study found that teacher-reported support between staff and among teachers and students predicted higher average levels of implementation. Teacher-reported administrative leadership predicted greater growth in implementation across 3 years. Findings offer implications for an ecological model of program implementation that considers school-level contextual effects on adoption and sustainability of new programs in schools.