As an adult, when I go into a teen/adult class, I have the same worries, that some of the teens will think that I'm "weird."
The fact of the matter is that everyone is there to learn the same things. At the start of a session, everybody is a little "up-tight" about the other class memebers. But, after a few classes, everybody will get to know eachother and you won't even reailze the age differences.
Private lessons are another problem. They typically run $30-$40 of a half-hour, and can cost much more for some teachers. On top of it, the teacher is devoting all his/her attention to you, and that can be bothersome, and make you nervous. Too much attention can be frustrating, because you hear about every little thing you do wrong.
Try your teen/adult class. I feel sure that after a few classes you'll be very comfortable with everybody.
Good luck! BalletMaster[/i]