I'm not sure a "net nanny" program would block an innoculous web site on which a participant chose to post tasteful nudes.

You seem to be trying to argue that the parents are at fault or intended for the kids to see the pics. There doesnt seem to be any evidence for that. Accidents do happen.

Again, I'm not saying they are right to fire the teacher. The opposite in fact. I just don't see how any one can be assigned blame here.