Bring in the clowns!
I suggest they'll scare the malefactors.
There are eighteen slides of clowns on that link.
The kids of course would have met the individuals and watched them acting in clown suits, so no shocking of children.
Meantime, I'm following along, and I get farmerman's take, to date, whichever thread. I see his point but am chary.
I also remember going to Mexico in the sixties and Guatemala in the early seventies and seeing guys armored up sort of all over the place.
I'd rather find another solution.
I don't say every security guard is a clown, really, being a clown takes talent; or every clown is a natural security guard. Just that armed guards at every school is something my hundred year old aunt who taught in a school house on the san juan islands in the 19teens would frown at. She lived many years past that time and was a pithy speaker.