> There have to be exceptions to the rule, of course. But how people treat each other comes more from who they are than what stage in life they're in.

Yes, but I think it's misleading to call high school and college "stages" of life. It's not that people act immature in high school, because they're at a certain age, and by "college age," they've matured. It's that the experiences themselves *cause*, or at least trigger, a lot of maturity. If you don't go to college, moving out of the house and becoming financially independent does the same thing. You get hit with the real world and suddenly discover first-hand what's important in life. You discover the cliques and petty rivalries of high school just don't work. You discover how you actually have to live when you can't just fall back to Mom and Dad. And so on.

Some people do mature faster than others. Some are nice at young ages, and some never stop being mean. But as a broad generalization, I think getting smacked upside the head by the real world is what does it for most people. In our culture, that doesn't happen very often in high school, but it happens sometime in the freshman year of college quite a lot, probably because most college students have just moved out of home and also because the institutions themselves expect more maturity and personal responsibility of the students and don't waste their time with students who can't grow up.

It happens most dramatically for the popular snobs in high school. They get to college, discover the showboating that's always worked for them falls flat, and have to rethink their social behavior. Some never do, but enough do that college environments tend to be so dramatically different from what you find in high school.