one thing relating to this to keep in mind in deciding between regular public school, charter school, and private school is that charter schools are still public schools and as sucy, FAPE applies so they'll have to provide any special education/IEP/504 accomodations that are required for him, whereas private schools may choose to provide that, but aren't required.
this may be old news for you and/or exactly what you were talking about, I just wasn't entirely clear from your post exactly what you meant & just wanted to be sure, so please accept it in the spirit of being helpful just in case it isn't known that it's intended as and not in the spirit of being an insufferable know-it-all that explains shit you already know to you that I'm frequently perceived as