I am a college junior, and still have trouble believing I am already three years out of high school. I guess that counts as a semi-answer to the question. ^^
As someone pointed out, many of the people that matter in your life come from high school. The friends you keep from high school through college are the ones that will probably stay with you for life. I know it’s true for me.
Also agree with @Piper_Brianmind high school are actually great years in retrospect. I was told college were going to be the best four years, not HS. But it wasn’t really true. College is a whole other ball game. You turn into a responsible adult, in theory, and you learn to deal with basic “adult” stuff, like bills, fighting bureaucracy on a daily basis, living alone, doing your own dishes. One word: independence. It just turns out you sort of feel less free when “independent”, because you deal with so much more stuff that your parents took care of for you in HS.
On the other hand, growing out of high school also has its benefits. The whole thing about “finding yourself” certainly rings true. I am a completely different person now than when I graduated from hs. It does bring a certain peace of mind. “Maturity”, if you will. ;-)