we were required to keep our classroom doors locked at all times. They would open from inside the room, but not from outside.

Seems like a good idea.

there should be a key for principals, and vice principles to have an entry key. All entry to schools should have safety doors that cannot be breached by a gunman if locked. The fact that the shooter was able to shatter the doors and enter so easily is a problem.
We have the technology to protect schools with making them prisons.

It may cost more to have certain plexiglass doors and lock down doors. Cameras are small enough and cheap enough to cover entrances.

and and the security doors are not needed. Get rid of the damn guns. That's Job 1. No more defensive measures, just get rid of the guns.

Then doing what is sensible and just banning these fucking things.

well that and a controller.

not only did the doors lack a lock but they were mostly made of panels of glass. Even if you locked the door from the inside, a glass panel could be broken and the door easily unlocked.