This study reports on aggressive outcomes from a cluster randomized trial of the Promoting Alternative Thinking Strategies (PATHS) curriculum. Fourteen elementary schools were randomly assigned to intervention or control condition and third grade students were followed through the fifth grade. Teacher and self-reports of student aggression, conduct problems, delinquency, acting out problems, and social information processing (SIP) variables were collected. Linear change for each of the SIP variables was noted with control students demonstrating increased normative beliefs about aggression, increased aggressive social problem solving, increased hostile attribution bias, and increased aggressive interpersonal negotiation strategies over time while PATHS students remained relatively stable. Teachers reported significant curvilinear change in student aggression, conduct problems, and acting out behavior problems; all favoring PATHS students.