As a teacher (with lots of experience in the Foundation Stage) I know that part of the job is sorting out differences between parents. The ballet teacher should have dealt with the situation, you should not be moving class because of the outrageous behaviour of one parent. She should have spoken to the parent after that class. It annoys me when people say that you can't teach when children are messing about. Children mess about, pushing the boundaries and having fun doing it are all part of child development. Having good behaviour management skills and strategies to keep children on task is an essential part of being a teacher. Your child should keep doing what she enjoys, perhaps work with the teacher and develop some kind of treat/job for your daughter to have/do (even something small like helping put out or collect equipment). I hope this gets resolved for you soon.