I think that you can learn a lot from being in choir. You can gain skills that will definitely help you in the future whether or not you enter into a career in music. High school is about gaining as many experiences as possible. You can specialize when you get to college, but if you experience a lot of different things now, then you will have a better idea of what directions interest you.
That said, what you can learn from being in a choir (aside from how to improve as a singer) is how to work as a part of a team. Choir is not a solo activity. You have to listen to the choir director as well as to each other. A good choir functions as a single unit in much the same way as a successful sports team, military unit, or corporation. Teamwork and team building skills can help you in many areas.
You can also learn self confidence. As a singer in a choir, you will perform in front of audiences. Becoming comfortable singing will help you be more comfortable speaking in front of a crown, giving presentations, and going on interviews for colleges or jobs.
Lastly, choir teaches you dedication. You commit to a time to be at rehearsal and you are expected to be there even if you have homework or something that you want to do instead. If you stick to that commitment you will learn how to manage your time and how to maintain a dedication to something - skills you will also use both in college and in life.