I may have to go to court for permission to pull my son from private school and put him in public

My son has been in private school for 3 years and so far things are getting worse. I have split custody with his dad and in our agreement I allowed him to keep attending private school and his grandmother covers the tuition. My Ex and his mom emotionally abused me for years. And I'm finally standing up for myself. My son is 16 and I private schools and we have problems. Private schools are not legally required to adhere to an IEP or 504. Some may but they are not legally required to. My son has ADHD and he's been managing okay without his accommodations he had in middle school. That changed over the summer because he was hit by a drunk driver on his bike and he suffered a TBI from it. He also has a lot of chronic pain physically. His focus is worse. It takes him 10 minutes to get to the 3rd floor because of pain and they refuse to let him take the elevators because it's for "staff only" and he can still walk. He gets detention every week for being late. They won't accommodate him at all and when I talk to his dad about pulling him he just goes on about how dumb public school is and that this will make him stronger in the end. I feel like I'm going to have to go through court to get permission to pull him from school and put him back in public because at least there they legally have to accommodate him