Although that’s probably true (heh), you don’t need to literally include cursing to make teenagers sound real. Network TV doesn’t have a lot of cursing, but it has widely accepted representations of teenagers on a bunch of shows. Watch some TV for inspiration! Bad grammar, apathy, and crass-but-not-cursing language can all sound realistic.
That’s how I wrote the scene at first, but it just didn’t feel right to me. One thing I learned from an art teacher waaaayyyyy back in Junior College was, “If it’s wrong, but looks right, it’s right. If it’s right, but looks wrong, it’s wrong.” It “looked wrong” writing without the cursing. It felt right when I changed it. It’s just a personal thing with me, and if I had to change it to suit a certain audience I would, but I think there are times when the cursing works better, no matter my personal feelings. It really depends on the characters, and for those characters, the cursing was better.