I would be ok with some of these ideas
1) Pentration tests on schools books using an AR 15 in 55 62 ammo to see if they are gonig to help as cover / protection in a backpack
2) metal detactors in major school entrances and exists that are not fire exists with alarms if someoe breeches them with a metal ojbect
3) Break away windows in outer classrooms that are similar to plane windows that can be dislodged for easy escape
4) fire escapes to the roof with slides for another escape route.
5) If the shooter is identified during the breech a person saying his name over and over on a loudspeaker / john smith put down your weapon and leave--mulitple PA systems so he would have trouble accessing it.
6) A number of cast iron human vaults that are bullet proof.
7) bullet proof doors in classrooms with bullet proof glass.
8) teachers provided with smoke gernades in classroooms for emergency evac purposes.