Alot do "catch up"
My step brother attended special schools, wasnt entered for GCSE's, couldnt be left alone in his teens, has a lot of SEN/ND needs. However at 32, he has a degree, owns a house, and works full time. Yes he required support to get the house, additional support to get into uni and didnt go at 18, he was much older, and has needed support in learning to manage his income and priorities, but he has done it and is successful.
My eldest is SEN, attended a mainstream school but barely passed his exams, he went to college but hated it. Now he is working full time. The job role is min wage but he loves it. He still lives with me but is gradually learning to manage his income and im moving bills over to him gradually, and he has to pay me rent which i s reduce as we move things like his phone over. Hes now 22 and hopefully in the next few years we can get him set up on his own.
I was diagnosed AuDHD in my late 30's. when i attended uni. I spent my 20's doing dead end job with no direction or ambition. In my early 30s i decided what i wanted to do and did it, started uni at 36 and qualified as a nurse at 39, now i have a role in emergnecy nursing which i bloody love and will continue to progress in. It took me a while, but i got there and foiund something i love.
Theres some who will never move out of live unsupervised, but theres also facilities popping up all over. I live near a cafe that employs SEN/ND people. Alot of the staff have autism or DS. They only do 1 or 2 days a week, but they are working, and the local community attends the cafe (even though the prices are atronomical in comparison to other places).
But i think most ND kids do find their place eventually, it just takes them longer sometimes