As we grow new tests and tribulations are thrown in our paths, and we adapt to our changing environments. Some people make the choice to be part of the popular group in highschool, some people become bullies because they don't have happy home lives, some people strive for straight As, some people withdraw from public life. Highschool is a formative period for many people, and big changes don't often happen until we hit university, move out, or get into our first serious relationship.
But I have a strong disbelief that everyone changes. I know there are areas in which I have grown, but I find that the majority of my major personality characteristics have been around since I was a kid. Maybe it's because I don't feel like I've done a 180 that I have a seriously hard time believing that people who I knew way back when have miraculously improved. That little girl who was a troubled child grew into a troubled teenager, and even after the birth of her child she's still someone with serious anger issues and a tendency to lash out. Those bullies from highschool are still cruel to people for no abject reason, now they just take it out on their coworkers instead of the dumb kid in class. That guy who pulled every manipulative trick to get into my pants is still trying 4 years later and having the exact same lack of effect.
So when are people supposed to change? Do people undergo a miracle - or a lobotomy - at age 30 that solves all of their childhood and teenaged issues in one fell swoop? Somehow I doubt that there's an age cut-off for behavior corrections, as my philandering grandfather proved again and again throughout his life, but I sure as hell hope that there is. And if there isnt, I hope that I maintain my ability to ruthlessly judge people and to make the rest of them jump through hoops until they prove their worth. Even if they fail my tests, at least it'll be entertaining - for me ;)