We need ex military, they have to be on the offensive, fat mall guards are not going to cut it.
I also don't believe teachers etc should have guns, maybe as defense but we need bulletproof doors and windows in the classrooms (he shot out the windows).
We need an ALARM only for active shooter and an alarm all clear, when kids and teachers hear that alarm they lock down, kids go to the nearest class, the window should have a draw shade so you can't see in. You stay locked down till the all clear alarm.
These alarm switches should be accessible in a lot of places, not like fire alarms.
There should be video monitors and command station like in principals office with a push to talk phone with the school guard, the video will tell them where the shooter is so the guard doesn't have to guess when they will come under fire. Guard needs armor, they can't be proactive without body armor.