I’ve been thinking about how colleges would look at me. I don’t do great – I only have a 3.6 GPA after two years (I had a couple bad grades freshman year due to new teachers). I’ve taken choir my first two years, I really enjoy it and I do music things outside of school (musical, and a chamber choir that only about 30 of the 200+ choir kids got into). But it’s an easy class, and I don’t plan on majoring in music – so should I drop it for junior and senior year due to it not being challenging?
No, improve your grades and stick with it if its something you enjoy. Colleges like to see students perusing the arts and as long as the rest of your schedule is rigorous there’s nothing wrong with choir.
NO! Part of HS is to explore things you enjoy. Take higher level classes or just do better in the classes you are in.
Keep choir. It shows commitment, and some colleges in the Midwest have choir scholarships 
I sure wish I’d done choir in HS!
Remember that most universities have choir and singing groups also (you don’t have to be a music major) but just having the background is a big plus. Later on there are community groups (both singing and theater), church, and singing organizations such as Sweet Adelines (four part harmony–check it out now while in HS! Look up Young Women in Harmony). Singing is something you can carry with you for years–if you love it, keep it up!