There's a lot of talk from gun advocates these days to arm teachers and administrators in schools. Some say that if the Principal at Sandy Hook Elementary had had a gun in her office, she could have shot the man shooting her students.
Unless you have been in an active shooter environment, or you have been trained in an active shooter environment, you have absolutely no idea how you would react when faced with this type of situation.
Let's look at the shooting in Tucson when Rep. Giffords was shot. There was an armed citizen on the scene who could have taken the shooter out. Why didn't he? He could not ascertain who was doing the shooting. When you have people running around and children in the line of fire, the last thing you want to do is introduce another weapon and possibly shoot a child with friendly fire.
Unless you are a trained marksman, no, check that, even if you are a trained marksman, in that scenario in those close quarters, you run the risk of killing innocent people when you fire at the one who is doing the shooting. Unless you know what your field of fire is, and can be sure that field is clear of innocent lives, you do not take the shot. Period.
Those who want to arm teachers are talking with false bravado and are the worst kind of gun owner: those who shoot first and think later.