School-wide behavior problems can vary significantly from structured to unstructured settings. Often problem behaviors can spike during unstructured times such as lunch and recess and the use of Tier 1 positive behavior interventions and supports (PBIS) can be used to reduce student behavior problems in these settings. Using a token economy as an independent group contingency, this study aimed to reduce student aggression in an elementary school during lunch/recess periods of the day. Students had the opportunity to earn school "dollars" during recess for demonstrating prosocial behaviors in which they were told could be exchanged for incentives at a student store (backup reinforcers). Across all grade levels, student levels of aggression were reduced between 50 and 100% from baseline levels in a 3-month period. However, as effect sizes indicated, only some intervention groups showed significant reduction of aggression. Despite the limitation of access to backup reinforcers, we theorized that the effectiveness of the present intervention was due to socially mediated contingencies among student group members as a result of receiving dollars.