This is a pet peeve of mine. Too many people write teen and YA character dialogue and inner thoughts as if they're hard bitten forty-year-olds. It doesn't ring true. I've noticed myself doing it and have figuratively slapped my hand numerous times for it.
If there is a reason for a character to sound like that, fine. For instance, I knew a kid whose Dad was an NCO in the Philippines back during the late seventies, early eighties. He grew up over there and saw a few things. With him, it would be believable.
Not so much from your average oversexed Nifty reader teen from the burbs.
This might not be the thread for it, but if hit my not funny bone and I had to bark.