This article describes a school-based aggression reduction intervention program aiming to impart highly aggressive adolescents with a learned resourcefulness repertoire, using Ronen and Rosenbaum's four-module self-control model. Intervention aimed to teach adolescents that aggression is changeable behavior resulting from how they think and feel, emphasizing cause-effect relations; to facilitate their identification of internal cues, sensations, and emotions and their links to behavior; and to help them identify and acquire self-control skills, e.g., delaying temptation, using self-talk, and planning steps toward achieving goals. Participants were 447 ninth graders: 167 underwent intervention, and 280 from the same schools received no intervention (controls). Outcomes indicate the model's efficacy in reducing aggression. In the intervention group, both objective and subjective aggression rates decreased significantly compared to baseline and controls. Hostile thoughts and negative emotions did not change, suggesting adolescents could now control these without behaving aggressively. Analysis attributed aggression reduction to increased self-control skills. (Contains 2 tables and 3 figures.)