I don't believe anybody is suggesting that you just give teachers guns and say "here go protect the students." I don't believe anybody in their right mind would suggest such a thing. The only way that the above points could be valid is if that's exactly what you did.
What people are suggesting is that you train, and the key word being just that "train" teachers who desire to be armed for the purpose of protecting their students.
Teachers as you describe them sound like wilting flowers weak and defenseless. I'm sorry but I strongly disagree with that insinuation. Teachers are tough. Just think what a teacher has to go through on a daily basis.
Again I am sorry for saying this, but it needs to be said, in an active shooter situation your daughter would be much safer if she, or another trained staff member, had the ability to fight back.
There's also the psychological aspect of it. The fact that her school would no longer be a gun-free zone would in and of itself be a deterrent. Murderers target gun free zones. So because the fact that staff is armed would mean but they would probably never have to use their weapons. Murderers are cowards chances are great that they are not going to go shooting people in a place where they themselves can get shot.
Remember the key to arming staff is training. And I'm sure there's a lot of teachers out there that would willingly go into training for it.