I think schools should have armed guards or a police presence, but if the teachers are okay with arming up too (on an individual basis) then why not?? Obviously they would have to train as a group for the scenario, but when I was in high school, I had a teacher that was a SEAL in Vietnam, and another that did armed boardings in the Coast Guard. Not sure how much more qualified you want them to get and both were great and down to earth guys. I'd put my money on either of them any day of the week. Obviously not every teacher is going to have that sort of resume, but if willing teachers are going to qualify and train, it will be a hell of a deterrent, and in the event that the worst does happen, you've got a trained team vs. a lone gun man (usually).