Arm The Teachers In America?

There is no need to arm teachers because of the shootings we have had. Let me ask you this question.  WHY ARE YOU ALLOWING ANYONE TO JUST WALK INTO THE PUBLIC SCHOOLS IN THE FIRST PLACE??? No one should be allowed to just walk in during school hours and that is a huge problem!  The shooters all have had mental problems now why are the schools allowing just anyone to come on in and walk around?