It is inconceivable that a person without a gun is going to stop a person with a gun. The person with the gun has the advantage. Those who are without arms are without defense and they are totally at the mercy of the one who is armed.
The armed person is free to shoot all he wants until he is confronted by another person who is armed. The sooner that happens, the fewer who will be hurt or killed. If they wait until police arrive, that likely will mean a few more injured, maybe another death or two.
Sounds like a logical reason to arm well trained teachers. Then again, dems don’t care about logic or lives. All they care about is power, to them guns represent a threat to their power.
Consider, a gun in the hands of a teacher or two is better than in the hand of a murderer.