He sounds just like my friend's son, now 10. He's 2e - HG with Written Output Disorder (as well as CDC).
My DS8 has written output problems too, and a language processing disorder. At school he has an IEP which accounts for this and allows for him to do less written work. He had the IEP before his formal diagnosis, so you may be able to get similar accommodations for your son if you don't have a diagnosis before he returns to public school. It would depend on the school and on the team, I guess.
Good luck
