18 yr son ehcp

Hi I would like to ask if anyone has been through what my son has with regards to college in March my son got withdrawn due to sleep and ASD and ocd he was struggling with the course and also the pressure that went with it we went to doctors as I was concerned where this coud go they give him mitrazipine and reference him to sleep specialist who dignosed him with delayed sleep phase syndrome and restless legs also said him had migraines my so became very Isoleted stayed in more and just so hard to watch but in September he went back to college and he was finding it ok but things got to much and so they said they won't reduce his timetable to afternoons this was in October 11 I have had means saying he can't carry on like this has he will miss too much I am at a loss as he can't help the way he is he only gesture to college 3 days a week the rest of the time he stays in his room to get himself ready for the next week if they withdraw him I don't know how he will take it has anyone been through this just not sure what his rights are thank you  for any help.