"I think that having only one door to a classroom was a shortsighted policy from the first . . .".

Especially in pre-sprinkler days. I've seen too many schools that have kitchens for use in what used to be home ec classes which now are called food arts (or something like that) and the way out passes in front of the stove--the most likely place for a fire to occur in kitchens. Many of the designs are poorly thought out with an eye to cost-cutting as opposed to safety. Schools have evacuation plans but usually those plans involve escaping fires and not attacks by armed people. The world has changed, but not that much. The following link to Wikipedia contains 'events' involving deaths of students and staff going back to the 1700s.

http://en.wikipedia.org/wiki/List_of_school-related_attacks