Good comparison however, I think there might be a better one. Public schools are limited in what they do - mostly by choice. Home schools and private schools have a lot more latitude in what they can do. A studio that is part of an organization may be limited in what they can do but the independent is not.
Home schoolers (good ones, at any rate) aren't typically worried about what grade level kids are in. They are very aware of what state standards are being used but just don't feel bound by them.
Instead, they are concerned with the mastery of a skill. You simply don't move on to the next concept until the foundation has been laid. Math and reading are foundational and each step requires mastery of new concepts and material. Science and history are taught in layers - material is repeated in more and more detail.
With public school, the teacher is frequently concerned about getting the kid through the grade they are in now (when they will become someone else's problem). Home schoolers are concerned with the end result.
We have the choice when we promote students to recognize a level of mastery or simple time in grade. I'd like to think we are recognizing a level of mastery.
Before the hate mail comes - as a home school parent, public school teacher and now private school teacher, I've laid this out in gross generalities to make a point. There are many good public schools (and public school teachers) and bad home schoolers. Use the analogy as it was intended, por favor.
Take it out on the heavy bag,