I think if you don't like the way your teacher works, you should switch teachers before considering quitting lessons altogether.
I've self-learned for a long long time before I took up formal lessons and trust me, I know what kind of bad habits and small mistakes can haunt you after that kind of learning.
You don't have to just learn to play the piece, try to analyze it and understand it's structure if you're so interested in composition. Ask your teacher for help if necessary. Also try to learn theory outside classes from books or WWW.
Experiment at the piano and fool around with the notes at home.
But if you have a teacher, you have someone to turn to when thing go sour and to point out your mistakes before they can become a problem.
If you feel that you are not making progress with your teacher, talk to him and speak your mind, if that still doesn't work then just switch to another teacher, there are both good and bad teachers after all.
But I would think twice before quitting lessons altogether and going through the painful and frustrating process of self-learning.
Hope it helps
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