A number of studies on lockdown drills yielded largely consistent findings about their impacts, whereas findings related to the effects of active shooter drills are less uniform. The research also demonstrated that lockdown drills, though not active shooter drills, can help participants build skill mastery to be able to successfully deploy the procedure. Differences in how drills impact participants and whether they cultivate skill mastery are largely attributable to the type of drill being conducted. This review suggests that employing clearly defined drill procedures incorporating best practices, coupled with instructional training, can help schools prepare for emergencies without creating trauma for participants.