An issue generated by the prospect of teachers carrying firearms is the problem of weapon retention.

Anyone trained with weaponry should understand that, when you are carrying, part of your attention must be on the weapon at all times. The way you stand, sit, walk, and interact with others must take into account good weapon retention practices.

Carrying a firearm is a bad idea for teachers because a teacher's focus should be on pedagogy, not on positioning oneself so that a student doesn't have easy access to your firearm.

The fundamental problem with guns as a deterrence is I doubt the active shooters care if they die. And where are these guns? Seems like by bringing them into the school you made them more accessible.