The study reports social-cognitive outcomes of interventions in a cluster-randomized school-based aggression prevention trial in low and moderate resource urban communities. Targeted social cognitions were aggressive responses, aggressive/prosocial fantasy, and normative beliefs supporting aggression. Participants were 1,484 early elementary school-age children selected for aggression above school medians. Schools received no treatment, curriculum plus teacher consultation (Level A), or Level A plus small-group training (Level B) over 2 years. The Level A condition changed the social cognitions supporting aggression in the desired direction but only in the moderate resource communities. The small-group component did not appear to add to the effect of the Level A condition. Findings suggest that early prevention can modify children's social cognitions in moderate resource communities.