I am a sibling of a severely disabled child. He would have turned 50 last month.
When he was born in the late 1950's, it was suggested that he be institutionalized with other kids like him. That was just what was done. My parents would have no part of that. We (as a family) provided for all of his daily needs... he was fed, bathed, diapered, dressed, entertained, etc. There was no such thing as disposable diapers back then. It was only closer to the late 70's and early 80's that disposable adult size diapers were available for a small fortune. For 25 years my mom (bless her heart) washed cloth diapers in a Maytag wringer washer. As he grew older, she made most of the diapers herself out of old baby receiving blankets, towels, flannel sheets because baby diapers were too small and the premade adult diapers also cost a small fortune.
It was only until he turned 19 years old and he could no longer be covered by my dad's medical insurance through work were "doors of opportunity" (for lack of a better word) opened. Suddenly he was eligible for month cash and food assistance, education, respite care, etc. In many, many ways it was a God-send to our family. Though she never would have admitted it, I know that it gave my mom a lot more freedom during the day for herself and for appointments and errands. She could even go to lunch if she wanted, alone, without having to worrry about him.
As far as educating him, he functioned at a 6-month-old level so he was never be able to speak, read or write. But he did get socialization with other people, students and staff. He was a people person, the more attention he could get the happier he was. He loved the 1-1/2 hour bus ride a.m. and p.m. since he loved riding in the car. He got therapy with music and singing and he was in seventh heaven.
In my opinion, though, sometimes it got to be more of a hindrance than good. The teachers thought they were miracle workers and through their efforts, suddenly a severely impaired student would **poof** become Einstein. What was the benefit to my brother to teach a blind, severely impaired child to manipulate his wheelchair? Sure he could operate his wheelchair -- WOW -- but he had no fear or understanding of danger of where he was going in his wheelchair as he headed for a flight of stairs, the street, the hot stove.
As I see it, your child will benefit from public schools such as 1) free physical and occupational therapy; 2) networking with other parents. This will also allow you some free time during the day for yourself, to work, run errands, etc. And as Valerie said above, your state might not give you the 'choice' of public schooling and home schooling. Seems unfair that they feel they can 'play God' and dictate what's best for your child, but they can if they choose to do so.
My prayers and best wishes go out to you and your son. Just know that if you ever want to talk, vent, etc. I'll help out any way I can.