My thoughts on this.
Teachers are people like everybody else. Some believe in the 2nd as much as everybody else who does, some don't.
Let those who believe be armed on their work. And the next attempt of a mass shooting in a school may very well end up differently.
Better to have a gun and not need it, than to need it not have it.
All things considered, it's still better to be judged by twelve than be carried by six.