I am an advanced clarinet player, so i know all about notes, pitches, and what not. I was just wondering if just anyone could learn how to sing, or must you have singing capabilities before you try to take classes. I would like to know because I really love my school choirs, and maybe I could take classes and join one of them. Thanks

Not everyone will always be able to sing to the same standard. It is possible for someone to have a ghastly voice, or to simply not be able to hold a note.
However, you won't know until you try, and preferably try with a bit of training for your breathing etc. Why don't you talk to whoever is in charge of your school choir, or maybe go to an audition? I wouldn't pay for private tuition, until you get some personal advise from someone who is going to give you an honest opinion.
And having said that, ultimately it all depends on what you do with your voice. NO ONE will ever be able to sing all kinds of music well, so even if you will never sing in a musical for example, maybe your voice is suited to rock, or rap, or whatever personal style you may develop. Look at Rex Harrison (My Fair Lady, if you haven't seen it, try renting it, it's great fun), he absolutely could NOT sing, BUT he was a great musical star, performing songs in a sort of declamatory style that's almost-but-not-quite singing.
You don't have to be fantastic to enjoy singing.

Thank you very much. Very informative.