Schools are what sociologists call total institutions. They consist of rigid status hierarchies, and people are forced into repeated interaction with no possibility of escape. Bullying is a typical outcome of total institutions. Interestingly, I read the hypothesis somewhere that many people become libertarians because they hated school; they experienced first-hand the ugliness due to lack of freedom.

As an adult, if you hate your peers at work, you can always go find a new social circle. Somehow, while at school, both the school and family discourage this. So, an excellent piece of advice to students: try to have friends who are from different places (i.e. not just your high school), and even better if they are older than you. When I was kid, I always used to hang out with my cousins who went to college, and they were so much more kinder, smarter and easier to talk to. That saved me a lot of sanity.

Tellingly, the other classic example of a total institution? Prison.