I'm a bit of a misanthrope so I guess my point of view will diverge from norm a bit.
I'm a highschooler too; I'm an incoming senior. My school is at a well to do, low crime area with a diverse student population. The teachers are dedicated and the API scores and like are all top notch in the state.
But are people annoying and stupid there too? Yes. Absolutely.
People are cowards. They're not evil. They're not good. They're just cowards. They make fun of you because they're afraid their compatriots will turn on them. They do retarded things that they shouldn't do because they should know better because they fear. Whether its social ostracization or the simple fear of not fitting in, people do all sorts of crap.
As for how to deal with it? Ignore it. You'll meet innumerable people like that. If you want to try your hand at converting them, the only thing you can do is give them something more terrifying. People don't gain courage. They merely find a bigger monster in the closet. Fear of eternal damnation keeps a lot of people in line, for example.
High school is more immature than "life" as a whole, though you'll never escape the idiocy. What changes as you grow older is that people, now "adults", gain enough fear to keep them from doing the stupid things they did in highschool.
Sorry for not being more uplifting. But that's my two cents.