This tragic incident was not an isolated one. Apparently this girl had been molested by these boys for some time, and it was not the first time they had stripped her and humiliated her. Why they picked on this particular girl is not known but thye could probably sense that she was weak.
Parents have to take a large proportion of the blame for the actions of these boys, however the school was absolutely to blame. Apparently everyone knew this girl was molested but noone did anything. The class should never have been left alone, not even for 5 mins.
Me being a parent, I would incrimminate myself on here, the only thing I should
say is, their only hope would be the police to find them first.