Don't just STAND THERE - DO SOMETHING! That has become the mantra of the political class. Any more gun laws will just make the sheeple feel more safe even though nothing really has changed.
One thing to possibly consider that might save lives: I was in a nursing home several months ago when a fire drill was called. A central button was pushed that CLOSED all doors to patient rooms. Of course, this was done to stop the spread of a potential fire. Perhaps, something similar would work in a school if the doors were bullet proof. Is this a total answer? No, but it might be a starting place for some discussion.