I had a number of friends at the barn who were in private schools (one was Lutheran and the other ones were all Catholic schools) and their schools were worse than my public school.

For the most part, I think that a lot of what Hollywood shows us is the very typical exaggeration for the sake of the point. But there are still cliques, there are still prejudices, there are still groups and "group warfare". Most of it is good-natured competition, some of it is meaner than that.

But you'll find there's a lot of variation, in both private and public schools. At my school, we elected a Down's Syndrome kid as Homecoming King because you know what? He was an awesome kid. He worked hard, he was nice to everyone, and you know what he bloody deserved it. At our neighboring school, he'd likely have few true friends outside other special ed students, and if he had ended up in that situation, it would have been to make the school look good.

From what I've seen, it's not a "public/private" issue. It seems to be more of a demographic issue. In schools with a more homogeneous demographic, I've noticed more of a "Mean Girl" attitude. In schools with a more diverse demographic set up, there's more physical fights, but the general attitude is more welcoming and laid back. But these are just observations based on the area I grew up. Other areas could easily be different.