An effective evacuation of buildings is critical to minimize casualties due to natural or anthro-pogenic hazards. Building evacuation models help in preparing for future events and shed light on possible shortcomings of current evacuation designs. However, such models are seldom compared or validated with real evacuations, which is a critical step in assessing their predictive capacities. This research focuses on the evacuation of a K-12 (kindergarten to 12th grade) school located within the tsunami inundation zone of Iquique, Chile. An agent-based evacuation model was developed to simulate the evacuation of approximately 1500 children and staff from the school during a global evacuation drill carried out for the entire city. The model simulates the motions of heterogeneous human agents, and the simulations were validated using video analysis of the real event. Resulting error estimations between predicted versus measured flow rates and evacuation times are 13.5% and 5.9%, respectively. The good agreement between the simulated and measured values can be attributed to the known distribution of students and staff at the start of the drill, and their known exposure to emergency preparedness protocols. However, the results presented herein show that this mathematical evacuation model can be used for logistical changes in the emergency planning.