A variety of factors are associated with the likelihood of reporting guns at school; however, mixed empirical findings hinder our ability to inform policies to reduce school violence. Additionally, many of the established factors are difficult to change over time, and limited attention has been devoted to more malleable factors such as anonymous reporting. To better understand how to improve the likelihood of gun reporting at school, we drew from three waves of survey data from 3,633 students in St. Louis, Missouri. Using a multilevel model, we find that perceived risk of victimization and the availability of anonymous reporting increase the likelihood of gun reporting, while negative peer commitment, self-reported delinquency, and victimization decrease the likelihood of reporting. Additional analyses suggest that independent of known risk factors that inhibit reporting, increases in school climate and improvements in availability of anonymous reporting can increase the likelihood of reporting guns at school.