Hey, I just read an interesting article in one of the dance education magazines that are strewn around the school we take our kids to...the gist was that a child who is obviously advanced in dance should not be moved up overall, but allowed to take 1 advanced class during the week, so that they can try to stretch themselves. Other classes should remain at the regular level. Not sure I agreed with all the remarks, such as 'this child won't be able to socialize at that level', which I think completely ignores the possibility of intellectually advanced children who are also advanced in dance.
Otherwise the approach seemed to make sense, give the child some taste of not being the top of the class, a chance to stretch themselves, some time to be around more advanced students to emulate and have as role models, but not every single class so that they wouldn't feel stressed too much, and fall off on their own self confidence...
Not sure if that would fit your bill, but might be worth discussing with your school.