Background: A link between aggression and disciplinary actions has been established; however, specific associations between reactive and proactive functions of aggression and disciplinary actions in the elementary school setting have not been evaluated. A better understanding of links between functions of aggression and disciplinary actions could directly inform whom to target and how to intervene to reduce infractions at school before more serious consequences (i.e., suspension or expulsion) occur. Objective: The present study evaluated unique associations between reactive and proactive aggression and increases in disciplinary actions at school over the course of 1 year. Methods: A sample of 173 elementary school-age youth (ages 8-10, 55.5% female) participated in the current study, with teacher and student reports as well as school record data collected. Results: Correlation analyses indicated that both reactive and proactive aggression were associated with increases in disciplinary actions; however, the magnitude of effects was stronger for reactive aggression. Further, path analyses indicated that when simultaneously evaluating reactive and proactive aggression, only reactive aggression was uniquely positively associated with increases in disciplinary actions. Conclusions: Reactive aggression appears to be the function of aggression to target for the prevention of disciplinary actions in the elementary school setting. Findings and their implications for intervention and future research are discussed.