Already been done.
The door latches are on electronic timers and are only open for entrance in the morning before school. If a student is later they need to use the buzzer and then someone in the office will release the latch electronically. Of course, they are glass doors with no anti-shatter film. As I pointed out t the principal, there isn't a door in that building that I couldn't open with a PU truck (as in, drive through it).
Of course, security wise, I have one of the worst rooms in the building. My classroom opens into a central quad that all of the, main, outside doors, open into, no matter which side of the building you come in from. The only way out of my room is into this open area where as, most of the other classrooms have a window to the outside and are on separate halls with exits to the outside.
To make it worse, I, and the other technology teacher, have several large windows open to the quad. For standardized testing purposes, the rooms are internally angled in such a way that there is no place in the room that cannot be easily viewed from these windows.
Last year I had curtains on those windows, both for security and to aid in classroom management, those windows make it hard for students to stay on task. This year the district decided that the windows cannot be obscured in any way. The new superintendent doesn't like the way it looks with the curtains visible when people come in the school.
Of course I was failing every ALICE drill because my students cold be seen from outside the room; the room was designed so that would be true (
A-L-I-C-E, the acronym for Alert, Lockdown, Inform, Counter, and Evacuate). The decision was made that I would be allowed to put the curtains up on the days we were having the drills; however, I am to remove them immediately after the drill. Anyone with at least a half of a wit can see the problem with this; but at least I am not getting marked down for a failure to respond appropriately during the drills.
I did point out the security problem and was told, "That's not really a concern." Of course, statistically, it's not. The odds of a shooter incident in any particular school hovers near zero. The trouble is that when it goes wrong, it goes terribly wrong.