I can't remember a single classroom from 1st grade thru high school that had 2 doors... and very few in college. The cafeteria usually did, but that was a special need.
I see your point, Ebbie, but I sincerely doubt that it would make a significant difference in terror attacks. Sure, 2 doors in case if fire would help... and new schools might be designed a bit better.

I suspect that older schools in poorer areas need to spend that money on other things.