I would imagine that most liberal teachers would choose to not take the training, nor carry a firearm, but then again, many liberals became first time gun owners thanks to their own leaders.
When push comes to shove, if someone is gunning for them, they might just be forced into doing the right thing. But to your point, I would be worried that a lib teacher with a gun might come unglued if the class became unruly and ended up shooting students in "self-defense". That, or shoot a student that is wearing a MAGA hat.
No one does "triggered" like a liberal . . .