Illness and injuries are common among students and school staff. Therefore, school nurses must be prepared. In this study, a 16-hour scenario-based emergency preparedness course for school nurses was evaluated for its effectiveness. Effectiveness was measured by (a) traditional methods (written exams and confidence surveys) and (b) skills and performance evaluations in simulated emergencies called On-site Mock Emergency Scenarios. School nurses who completed the emergency preparedness course showed significant improvement in knowledge, confidence, and On-site Mock Emergency Scenarios scores that measured each nurse's ability to apply knowledge in simulated emergencies.