TexasCHLforum.com

not really relevant to the question asked, In the scenario you're describing it's most likely at it would be one of your students who is doing the rampaging.

You should probably ask yourself if you would be prepared to shoot one of your own students both emotionally for yourself and what would likely be the public outcry at a teacher shooting a student under any circumstance. I can't conceive of why you might get in trouble in the court of public opinion for shooting a rampaging student, but the court of public opinion is a fickle thing and all it takes is enough pressure on one politician and you're in the hotseat for doing what's right.

As to the other issues, I would request permission to carry in writing if he wants you to help, but when it came down to the wire and it really went down I'd probably arm up and help out anyway. the "immediately necessary to prevent serious bodily harm" should insulate you from prosecution.

all other things being equal, IANAL.