The answer is easy - society has changed so much that behavior like that is common place.
I was listening to the radio the other day and the top three offenses in school in the early 1960's were things like being late, talking without raising your hand and skipping school. Now it is assault, drugs, and being drunk. Heck, you can't even say the pledge of allegiance anymore without getting sued. Kids have no respect for authority because liberals don't want them too. All of it snowballs into things like kids raping other kids.