I have no problem with arming school teachers, so long as they voluntarily agree to be armed and properly trained; this training should be based on police training and include safe handling, marksmanship, legal issues, when to shoot and when not to shoot, etc.
One issue I can see is if a shooting starts, kids will flee and the halls will be crowded making a god shot difficult or impossible. Of course, the teachers would have to be held legally responsible for their actions, just as any legally armed civilian is.
