Maybe we could make schools just like airports with metal detectors and pat downs for security? But it would be kind of expensive and I don't think it would ever happen.
Could part of the problem be the public indoctrination/education system needs a complete overhaul in the US. I started school in the 1950s we had some pretty mean teachers that would abuse physically, I remember when I was 10 being knocked around and shoved up against the wall in the back coat room by a teacher trying to get a confession from me. So it could be that maybe if a more in depth investigation could lead to some reforms in the US school/indoctrination system. I think with all these acts of violence a serious look at what school mandated by the state is all about, what it is trying to accomplish, and such is called for.