I've been reading this thread through and suddenly had a thought.
What if a mother decided it would be better all around if she lived away from home, nearer to her work, but so the family didn't have to move? What if she didn't see or speak to her 11 year old for the first 6 weeks, to help them adjust, and then saw them for exeat equivalents - so maybe 3 - 4 weekends a term?
Said child is still in their home, with their dad, who, say, works school hours only, and available to support extra curricular life, from sports to friends having sleepovers.
That mother would be thought baffling and bizarre, and no one would think it was the right thing for the child.
My dad, and 2 of his brothers all boarded. All completely screwed up. The one brother who went to the local school (they ran out of money) has become the most successful, and most content of them all. I know lots of other awful stories/ results, but obviously my dad is the one I've seen up close.
As to children with severe disability, the relevant schools are just the modern day equivalent of "putting them in a home", entirely necessary, and entirely different.