Reading all the comments on this thread about "not getting mature until 30", I can't help but think that maybe we've just reversed adolescence and childhood. These tween kids act like teens, and the teens act like children.
I can tell you one thing, though: if I ever have kids, they will NOT be like this. I happen to be one of those people who is gifted with not-so-common-common-sense.
I grew up around the conversation, "Who's the parent?" You are..." "And who's the child?" "I am..." I didn't always like it, but dang it, I turned into a 17 year old who believes in being a good steward of what you've got, not expecting the world to revolve around you, and not compromising yourself to fit into this stupid "lets all be hip and wear 100-dollar jeans and tennies" trend. I credit it to awesome parents who set boundaries, kept me out of public school and only let me listen to Christian music. Seriously. The music limit was the one of the smartest, kindest things they ever did for me (among many things).
Gosh, I was just having that conversation with someone earlier today!
From experience I can tell you that it's doable, in spite of the pop culture. Among other things, keep them away from the Internet and keep them away from television. And make sure they speak the King's English in the house, no matter what filth they wallow in with their friends.