Yes, IF said teacher chooses to do so and has passed advanced firearm training

I understand where you're coming from, but even advanced training can't fully prevent accidents. I remember a story about an experienced police officer who accidentally discharged his weapon in a school environment. It was during a safety demonstration, and thankfully no one was hurt, but it just goes to show that accidents can happen to anyone. How would you propose to further minimize the risk of such accidents if teachers were allowed to carry guns?