I read this book many, many years ago in elementary school. It is about a girl whose parents sign her up for ballet lessons. She doesn’t like ballet and is not excited to attend her lessons. She has an older sister who has been taking lessons for a few years already, and isn’t necessarily happy that her little sister is also taking classes. I remember a certain part where the younger sister is in the locker room and is mortified by the disfigured feet of the older girls in the ballet school.
In the end, she learns to enjoy taking lessons. This is really all I can remember.