I think with the initiation of minimal armed school protection that the whackos will decide to try anywhere that remains a gun free zone. They don’t want to be shot or arrested before they can get the first shot fired so they will likely head for any unarmed groups.
IMO, the kids in Israel could use the type of protection you are suggesting but here, I don’t think we will need it. If sending your kids to school was that dangerous, mothers wouldn’t do it.
I agree about the path of least resistance. But I also don’t believe the basics of what I suggested are not that costly or extensive....door, shutter, door bolt....most outer hall walls are already concrete. Intercoms usually there....the wireless 911 station would be extra, though.....
If the nutjob doesn’t see the victims readily, he’ll move on where he might see them..