The high school where I spent 20+ years as a trade and industrial teacher covered over 10 acres under the roof on 3 floors, housed 3K+ students daily, and had over 100 outside doors with "panic bar" latches. EVERY one of those doors had to be unlocked and unobstructed when students were present, by fire code rules. All it took was a pebble or a textbook in a door jamb to disable the locking device that prevented outside access. The local drug dealers knew where all the doors were that were invisible to the security cameras, and they did a booming business hanging out in those places at class change time. Try making a building like that "secure" sometime!
