Arm a select few teachers in every school while posting signs of a well armed school.
Tough but best defense.
if somebody wants to go shooting, as these a-holes who will burn in hell, then they will go. they know they are not getting out alive. so I am not sure if that's a deterrent. its just less kids get killed. but still kids get killed. we shouldn't have tolerance for any. less is still some and ask the parents of those kids how they feel. our tolerence and expectations should be set at ZERO.
so not sure if that's a solution. just because someone has a gun, doesn't mean they know how best to use it in a chaotic stressful situation. its not as simple as pulling a trigger..... Police, Armed forces get trained for how to manage in those situations. they go through training. what if that teacher in the middle of a chaos, perhaps kids running, thinks they saw the shooter and shoot an innocent kid. will we say, well eventually they shot the killer, but hey we lost less kids and limited the damage.
its sad, a sad sad day if we have to have fully armed personnel and teachers to "feel" the kids are protected. feel not actually being protected.