I suggest you look up the actual statistics for school shootings. And I mean actual school shootings, not the kind of stuff that's defined as, "somebody fired a gun somewhere on school property at any time, and somebody died as a result" (which famously included a case of a guard suiciding with his duty handgun in a school parking lot at night).

It really is a problem that is blown up out of all proportion to the actual threat. The threat is there, sure; but a kid in US is more likely to be killed in a car accident on their way to school, than by an armed spree killer in that school. Those active shooter drills, in particular, save some lives, but they traumatize several orders of magnitude more. The notion that you have to be wary of a stranger who isn't even on school grounds for this reason is absurd.