I'm in favor of teachers being armed with nonlethal weapons. There are some high schools in inner cities that no sane person would venture into. But teachers are on the front line trying to do their jobs -- sometimes against teenage thugs that have a rap sheet before they're 13.
Pepper spray is routinely mentioned. But my favorite is bear spray. The propellant shoots about 60 feet, is wicked stuff, and leaves a burning sensation that, well, will stop a bear.
Of course, liberals will cry foul. Children, even as hardened criminals, have rights. But a teacher is not only protecting herself but an entire classroom. It's unfortunate it has come to this. But it has.
Added to the problem is the issue of personal rights and multiculturalism. Concealed weapons are allowed on some college campuses. Also, Muslim women can wear the all-concealing burqa. It will take a few more shootings before metal detectors are routinely installed in all buildings.