I like my ideas the best..Some states require gun trigger locks on guns so stealing or kids playing with them is useless.
In Indiana we hired off-duty cops. Every school up to college should have a real policeman on the grounds. It only cost 300 bucks a week and parents would agree to pay the little extra to provide real security for their kids.
If you are a gunman pulling up with a cop car parked outside you’d probably be less likely to try to go inside. Most of shooters are cowards that prey on the weak and unprotected then kill themselves.