Answer :
If my daughter has not complained about her progress and how she compares to the others in her class, I would agree with the instructor's assessment to keep her in the class. My daughter is young and dance requires many years of practice to master the moves correctly. It makes sense to continue to have her take classes. Unless she communicates that dance is not something she wants to do, keeping her with her friends is the course of action I would take. Some people definitely take longer than others to gain skills like dancing, so she will eventually dance more smoothly or she will determine that dance isn't for her and we'll stop lessons at that point.