It likely wouldn't make that much difference. There's been a news story, in which certain average Joes were put through gun training, they were given helmets and everything, and once they were done with such a thing, they went to an assembly about gun safety.
An actor walked in and started randomly firing these non-lethal pellets at everyone, the people, who likely didn't know these were nonlethal ammo, and didn't know that they two had been given nonlethal ammo got down immediately, but not a single one of them actually shot the actor. When later an explanation was provided and they were asked about their actions, they had nothing to be proud of, save that "they didn't get hit", and even so, tests showed, from looking for the dust and dents left behind by the "bullets" that a majority of them were, in fact, nailed in the head, some more than once.
You shouldn't give a teacher a gun, because not everyone actually has the nerve to shoot a gun, no matter what the situation is.