I was only talking about armed teachers and their probable lack of movement. Armed guards can walk around and pop up unexpectedly. So can armed sheriffs. So can armed police. So could well-trained, armed volunteers. So could armed administrators. Trying to bring a gun into a classroom to show off is not the same as intruding a classroom with intent to kill.
Of course there have been no massacres there. If your schools are patrolled by an army (as this sounds like) I doubt you would have any.
I don’t think you can extrapolate that to the vast majority of schools.
More efficient means are needed.
It appears that you are not familiar with Oakland gangs- They bring these guns to school to attempt to kill other gang members in school or on campus, not to show it off, but to off someone..I lived and worked there 10 years doing city security.