I spent a total of 14 years as an elementary and secondary school principal. About 10 years ago in a small, rural town in NE Oklahoma, on two occasions I took guns away from elementary school students. One was in the 3rd grader, had a .22 "sucicide special", cheap, break-top revolver that he had picked up at home and had brought to school as a "playground show and tell"! This little sucker was not menacing with it, just brought it to school and was passing it around on the playground. It was not loaded. This kid was expelled from school for one year and was taken into custody by the Sheriff Dept.
The second occasion was when a 5th grader brought a .380 auto to school. The gun was a cheap Raven, or something of similar type and quality. When I recovered it off the kid, it had a loaded magazine, and had one in the chamber. He had it in his coat pocket and was showing other kids how to "load" it and cycle cartridges through the pistol, again out on the play ground. He also got a one year "vacation" from our school and never did come back.
About this same time, I was at school armed when I knew I would have to deal with one of the "certifiable whack jobs" from the community. We ended up calling the sheriff to have him removed from the school ground. About a year latter, he murdered his wife.
Twenty years earlier, in Kansas, had to deal with a "whack job" at a school event. This guy was the town nut case, was sent away for an "evaluation", and upon release, took a gun a sunk a boat he and his father were in on a lake. Oh, by the way, he lived right next door to the school.
I don't think that the rank and file teacher would have the mind set to carry a firearm in a life and death crisis situation, I think they are just not "wired" right to take this kind of position. I do think that a large number of school personel would, however take on this responsibility and have the ability to deal with a crisis. I think the prohibition of concealed carry by appropriate people at schools is a grave mistake.
I've "been there and done that", and schools are definitly not a safe place. I'm afraid we are only going to see more tragedy in the future.