The present study explores the relation between academic self-concept, self-esteem, and aggression at school. Longitudinal data from a racially diverse sample of middle-school students were analyzed to explore how academic self-concept influenced the likelihood of aggressing at school and whether high self-concept exerted a different pattern of influence when threatened. Data include self-reported academic self-concept, school-reported academic performance, and parent-reported school discipline. Results suggest that, in general, students with low self-concept in achievement domains are more likely to aggress at school than those with high self-concept. However, there is a small sample of youth who, when they receive contradictory information that threatens their reported self-concept, do aggress. Global self-esteem was not found to be predictive of aggression. These results are discussed in the context of recent debates on whether self-esteem is a predictor of aggression and the use of a more proximal vs. general self-measure in examining the self-esteem and aggression relation. Aggr. Behav. 32:17, 2007. © 2006 Wiley-Liss; Inc.