Depending upon your state laws, you many not have to ASK to part-time homeschool. You may only have to INFORM your school that you intend to do so. I know that this is the case in some states. It is worth looking into if you haven't already.

I understand your frustration and you are right to be concerned. If you choose to advocate at your DS's school, change will probably not happen overnight. Sometimes it is a matter of finding just the right teacher or administrator (gifted teacher or coordinator) who understands why your DS needs something different.

You mentioned changing schools. Are there schools nearby that might be a better option?