I get a bit of the school security hysteria given that school shootings are a thing in our armed and polite society, but I find a lot of the
"fear of unknown people in a school" is just the general American weird fear of public spaces. If someone with a gun wants to kill a lot of people fairly randomly, they're going to, because guns let you do that, but otherwise public spaces are pretty safe because they're, you know, public, and filled with lots of people. "Strange danger" actually on school grounds is a pretty ridiculous thing to worry about, generally.
