I want that shooter praying I don't find him!
So how would that work? I live in Missouri, Second Amendment state. No permit is needed to conceal carry. No training is needed. Anyone older than 19 can conceal carry. Would teachers need to be trained, even though they didn't need training before? Would students be able to carry if they were older than 19? Would the school administration need to be informed if a teacher carries? Would the other teachers have to be informed who is carrying and who is not? You cannot conceal carry in sports stadiums; would that mean the armed teacher couldn't go to high school games? In the event of an event where the teacher is forced to fire at someone; should they hit a bystander then who is liable, the teacher or the school? Who determines the competency of the teacher to keep a weapon in school? After all, if a trained police officer in Minneapolis can panic and shoot an unarmed woman then why should we expect better results from untrained or partly trained teachers? How do we prevent the teacher who emotionally or temperamentally unsuited for the responsibility from being given it? How do you determine their suitability to begin with? How do you ensure they retain their proficiency? How often to they have to re-certify, in a state where they aren't required to certify in the first place?
You may believe you are capable of filling the role you describe. I don't have any reason to doubt you but what about everybody else? I may be an excellent driver, I believe I am, but it's not me I watch out for. It's the other idiots on the road.