I don't know, just a thought.
A logical one too really. I seem to recall watching a news report of a retired Marine who started standing guard, in full uniform, outside his daughters (or sons i guess) school. Even back when I was in high school in an area that rarely sees gun violence, we had a police officer (actually i think he was R.C.M.P.) who was in the school two or three days a week.
But here's the thing. As long as people can go purchase, legally or otherwise, high capacity magazines, semi-automatic rifles and kevlar vests, there really is no preparing for an attack like this. If a crazy person wants to hurt your kids, he'll find a way.
I can't imagine what world these kids are growing up in honestly. When I was in school there was no 911, terrorism was something that happened in desert countries to brown people, the drinking water was safe, and I didn't have to worry about being shot to death during recess by an M4 variant rifle.
what kind of life do these kids have ahead of them? Are they even allowed to be kids anymore?