It sounds like a lot of you kids aren`t taking lessons at all. This is great (and cost-efficient), but could limit your learning. A great way to improve your piano skills is the Hanon book of Virtuoso Exercises. It trains quite possibly every technique that a piano would ever need.

Be aware that this book won`t help your musical knowledge very much. Instead, it trains finger strength and coordination. I`ve been playing for 10+ years, and I haven`t yet mastered all these exercises!

i`m 16 now, started piano since 6...hmm... it`s about 10 years... how can a book help? i mean, u won`t know what u`re doin` is wrong until someone points it out to u, rite? and how would u know if u`ve mastered the techniques in that book? it`s up to yourself if u think u`ve mastered it, rite?
i think lessons are good if u wanna be good

Actually this really helps, especially for people who start piano at a later age. Your joints tense up, and that makes it quite difficult for you to play, but if you use this book and practice the excercises until you master them, then you will play soon with no stiffness, and also, you will improve technique. It is kind of like doing scales.