Child with Disabilities Dropped From Coverage?

I am a special education teacher. I have a seven year old student who has Down Syndrome and has had heart surgery. The mother went in to the dentist and was told his insurance was dropped. (Obamacare) He is also out of heart medication because of being dropped from insurance. The other siblings are still on the plan, but she was told this child was no longer covered. Is there something she needs to fill out in order for him to be covered because he has disabilities…or did he age out? Thank you for your help!