Thanks to everyone for your replies!

Just to clarify, this is a private school--and a tiny one, so they are pretty flexible--and they don't have to deal with state testing or regulations that only apply to public schools.

I totally get that in the public system there is a lot of red tape that is insurmountable.

I'm wondering if there is anything that applies to both public and private schools I might be missing--or anything else that is not a public school issue.

I have to admit that one of the reasons I had for trying this approach was because of the competition thing. It seems to me that it is fairly standard practice to accelerate gifted math kids one, two, or three levels while still calling them a whatever grader. Do the math competition people make them compete at the higher level?