LauraJane, welcome.
--as MON said, let them know that you need to meet with them. I'd also use the words "change of placement," as in, "We do not think a change of placement is appropriate at this time." I believe that in most cases they can't unilaterally move him-- you are part of the team that would make any decision of this kind, together.
--see if you can find an educational advocate in your area. You need someone who can quickly get you up to speed on your child's rights, but this need not be a lawyer. Our educational advocate comes to meetings with us and does wonders in getting things done cooperatively. Your state may have a Civil Rights Office that will provide this service for free, or you may have to pay-- but it is likely to be worth it.
--have you requested testing in writing? If your DS needs accommodations or services at school, they have to do an evaluation if you request one. You may want to look at the wrightslaw.com website or the Wrightslaw book, From Emotions to Advocacy, for details on how to do this.
--start looking into testing by a neuropsychologist, as well as a workup by a developmental behavioral pediatrician, apart from anything the school is doing. The developmental pediatrician would look for medical causes of behavioral issues and perhaps give you a better handle on medicating the migraines; the former would do a complete round of educational testing to figure out what the strengths and weaknesses are, and how to give the child an appropriate education. I wouldn't rely on the school to get this diagnostic information right; doing it privately is better.
Because it's a medical and behavioral health issue, you are likely to be able to get this stuff covered by insurance--call insurance first to figure out what they will do. If they won't cover it, there may be state or county funding for evaluations to determine whether there's a disability.
Hang in there.
DeeDee