Amen. We have that at our school. If someone like Lanza tried that - one, he’d not be able to get in. If he broke in with a gun, he’d be dead.
“Gun-Free Zones” are invitations to these mental cases. The shooters show great displays of cowardice, and would never attempt to shoot up a place that had armed, trained people.
Even the Ft. Hood shooter KNEW that the soldiers would not be armed in the dining hall.