It REALLY set a VERY BAD EXAMPLE for the kids in school that everyday they see teacher having a gun on their belt means authority. They will think having a guns means right and powerful which will make kids mimic (kids love to mimic) and try to get a gun in their own hand since it is popular!
This will create more problems than it can solve. If you see guns every where, do you feel safe? who knows when and where someone will become crazy, grab a gun from the teacher and start to shoot.
Smart Move.
Good Idea.