I can explain about specialist schools, because DD1 went to four at secondary.
All four were charities, so there was no profit making there! They just charged the LAs their costs. Even when they had to put up their fees, due to inflation (or like the recent increases in NI ers), some LAs refused to pay the increases. Parents sometimes had to consider high court action against the LA to get them to pay the fees.
The specialist speech and language schools had classes of 10 children, with a language based approach to the National Curriculum, no foreign languages, two TAs and a full time speech therapist per class. So children were taught literacy and numeracy in groups of about three, and the school used vertical streaming to group children by ability. The children had to be in the normal intelligence range. DD1 had to do foundation GCSEs due to her poor memory, but others could do the higher GCSEs. Children either went into college/university to do visual subjects like art, photography, graphics, etc or vocational courses like catering, animal care, horticulture, etc. Afaik, all DD’s friends were in employment in their 20s, had relationships, babies etc - because if you met them, you wouldn’t know they had any specific learning difficulties.
What is fundamental about special/specialist schools are the classes of ten, specialist SEN teachers and a differentiated approach to the curriculum. These cannot be delivered in mainstream classes of thirty with ordinary teachers. Some ND children have sensory processing problems and are overwhelmed by the sensory input in a class of thirty. They can’t learn. That’s why parents who can afford it, go for ordinary independent schools with experience of SEN, for the small classes and nurturing environment.
DDIL is from Poland. She tells me in Poland, DGC (who are both in primary) would have a staff ratio of 1 teacher to 10 children. If Poland can afford it, why can’t the UK?
As for the specialist schools charging 6 figures, they are likely to be residential and the children need high staff ratios like 1:1, 2:1, 3:1 or 4:1 care. These schools are just as much about social and medical care, as education. Even if you took out the education element, the care is still likely to cost 6 figures. These schools deem the children need say 3:1 care to keep the staff safe; and the children are either there for child protection concerns; or the family is on the verge of or has broken down. There may be child protection concerns about the siblings too.
All those posters, who talk about these schools being parents’ “preferences”, or say parents should have to cope with disabled children, they chose to have, are really saying:
“Let’s throw these exhausted women and the vulnerable siblings under the bus, in a situation I couldn’t cope with either!”
Speaking personally, DD1 went to specialist epilepsy schools, because it was cheaper for the onsite medical staff look after her in emergencies than call 999 three times a week. Then there were the knock on costs to the NHS of the rest of our family’s physical and mental health breaking down, instead of DH being a higher rate taxpayer and me an ordinary rate taxpayer! Closing the school down, as some propose to save education money, would have just cost the NHS more! Hint - DD2 has cost society probably just as much as DD1, in terms of the emergency services!