This study evaluated the short-term impact of a school-based violence prevention initiative on developmental processes thought to place children at risk for future aggression and violence and examined the influence of classroom and neighborhood contexts on the effectiveness of the violence prevention initiative. Two waves of developmental data (fall and spring) were analyzed from the 1st year of the evaluation of the Resolving Conflict Creatively Program (RCCP), which includes 5053 children from grades two to six from 11 elementary schools in New York City. Three distinct profiles of exposure to the intervention were derived from Management Information System (MIS) data on between classroom differences in teacher Training and Coaching in RCCP, Classroom Instruction in RCCP, and percentages of students who are Peer Mediators. Developmental processes that place children at risk were found to increase over the course of the school year. Children whose teachers had a moderate amount of training and coaching from RCCP and who taught many lessons showed significantly slower growth in aggression-related processes, and less of a decrease in competence-related processes, compared to children whose teachers taught few or no lessons. Contrary to expectation, children whose teachers had a higher level of training and coaching in the RCCP but taught few lessons showed significantly faster growth over time in aggressive cognitions and behaviors. The impact of the intervention on children's social cognitions (but not on their interpersonal behaviors) varied by context. Specifically the positive effect of High Lessons was dampened for children in high-risk classrooms and neighborhoods. Implications for future research on developmental psychopathology in context and for the design of preventive interventions are discussed.