Is it fair to ask for a director to change my role?

I am in a town summer production of "Footloose". Everyone can participate ages 7+. In last year's production of Bye Bye Birdie, I was cast in a large group role: with LOTS of little kids. This year I was cast in that same general group role as a townsperson. I am 14 years old. I am going to be a freshman next year. I went to the first rehearsal and I honestly felt like I was babysitting. They even said on the website that kids ages 7-11 could leave at 8:00. I asked if I had to leave or stay because I had the same part as them. They said I could leave, too. This made me a little angry: I was cast the same thing as the sevenyear olds. I am just about the only one my age. And the kids my age are in the teen choir. I worked really hard for the audition, did better than my friends, and prepared a solo piece and they got a better part than me. I know that I should be happy that I got in (with EVERYBODY else) but honestly I want to be challenged. I'm a born soprano and the stuff we're singing is like monotone alto. Would it be fair to ask the director if it's possible to put me in the teen choir instead? I'm a good actress and singer, but I didn't understand their decision. If I do ask, what do I say? I've had 7 people tell me today to say something about it but I don't feel like I'm in the right place to complain about it. Then again, if i I don't say anything, the play will be ruined for me. And don't tell me to quit. Once I commit to something I don't quit. Thanks in advance. Please help!