Unfortunately that all depends on the school... and if the principal is the same one, it doesn't sound hopeful.
Officially, in NC (where I am), the principal gets the final say on all grade placements -- they could theoretically put a teenager in kindergarten. I've never heard of it done, but it's not illegal or anything. Generally they place kids according to their age, which is one of the reasons we're planning on homeschooling for the long term here...
One thing you might consider is homeschooling up to a transition point - like homeschool 3rd-5th grades so you can approach the middle school instead of the elementary school (if 6th is the entry point for middle school there...) That would get you past the current principal anyway.
One of our options here is to wait until DS could reasonably be accomodated in high school and call him a 9th grader then. I'm not holding out much hope just because of what I know about our local schools, but in some districts (or even in some of our private schools or charter schools here) it might be a good approach.
