Start with crowding and go from there. If your school was small and everyone knew everyone, that's a vast difference. It takes just a few bullies (or worse, cr

Start with crowding and go from there. If your school was small and everyone knew everyone, that's a vast difference. It takes just a few bullies (or worse, criminals), who get a bunch of sycophants, to ruin the atmosphere. If you cannot remove them, nobody knows how to control it. Middle schoolers are as cruel as any people, just less sophisticated, so it's much more obvious. They form tribal social groups which fight, cut out people they dislike or judge, explicitly. Trying to remove that bit is nearly impossible. They do respect teacher authority, so an oblivious enough teacher can think everything is fine - or they normalized deviance.