Yup. Most people have said this already. Practice! Practice practice practicepracticepracticepracticepracticepracticepr acticepractice...
Just don't give up too soon. It'll seem really hard at the beginning. You'll feel like you aren't improving at all, but keep going! It will get more and more enjoyable. If you're willing to work hard and play for, say, an hour at least each day, you can get to playing some really neat pieces. Being able to jam with a band isn't really going to help you play classical, but if you want to jam with a band and you don't want to play classical, that's perfectly fine. Playing classical wouldn't really help you in a band, either.
Also, remember, when you get a little better at playing, if you're playing classical, there has to be more than just notes. You have to add dynamics (volume changes), articulation (how long a note is held), and all sorts of other things. That's where a piano teacher comes in handy.
Just keep working!
