He is wrong. An armed guard is an unnecessary and large expense and armed teachers works better. An armed guard is too easy to surprise with the first shot then there is that “gun-free zone” again. Multiple guards becomes prohibitively expensive. Just let it be known that teachers and staff may be armed. There will be no attempts at massacre again. Israel is the model. That does not preclude explosives but nothing really protects against that.
Is there some reason to have only -one- guard...