It may be that the safety protocols at Sandy Hook worked, and worked well. It appears at the moment, on what little info we have, that the lock down procedure protected many of the classrooms. As horrible as it is to think about, without those procedures many more of the classrooms may have been accessed by the killer, with consequential results. 20 children were killed, several hundred were not. Schools are designed with a heavy emphsis on fire safety, which means you can get out easily. Every exit is also an entrance. Doors and windows included. Even if we wanted to convert E occupancy to institutioanal restrained, an I don't think we do, it would take a very very long time.