Maybe a crazed gunman drill would be in order, you could even have the alarm do a special ringtone so the students would know not to run out and be mowed down like cattle, but to throw themselves out of the windows instead. The drill would cause only moderate casualties if propperly prepared.
Or alternately, you could make sure that guns were so unavailable, particularly to children and homocidal maniacs, that these things would be so unlikely to happen that drills would be unnecessary
Nahh, too advanced.