I'd like to get a better understanding of what you are aiming for @ehcpnightmares
Near to us there are:
A couple of different private SEN schools where there are about 6 kids to a class, very high adult to child ratio and highly personalised curriculum. In one of these the kids typically come out with no qualifications at all, or perhaps some functional skills certificates, but the focus of the educational effort is entirely on helping them to cope with the basic complexities of life, not getting qualified. At the other there is a bit more academic content in the curriculum and some of the kids do manage to get 5 passes at GCSE with a curriculum that just has 5 subjects of study - no where near a mainstream timetable.
- these schools are both massively full and oversubscribed with many more children needing them than could possibly be helped. Theoretically there could be self-funded pupils without an EHCP there - the fees are around £80,000 per year, due to the very high resources needed, but in reality when places are available the school will always offer the places to the state-funded pupils with and EHCP whose needs have been assessed, rather than a pupil whose parents want them to go there but who have not been through that process.
There is also a really nice, nurturing and non academically selective private school which has a "middle school" for years 4-8 and a main senior school that starts from year 9. Class sizes are about 22-24. a lot of the pupils have no SEN and are just from wealthy families but not likely to pass rigorous entrance exams, but every year they intake a significant number of "refugees" from the state system into their year 9 - enough that there are additional classes added to the cohort for year 9 compared to year 8. The education is mainstream, full curriculum but without the pressure to perform that there would be at an academic mainstream private school, and they get good GCSE results- not stellar, but decent. I don't think there are any pupils there who are state-funded to be there though, or if there are it would be a temporary arrangement for someone who really needed one of the SEN schools while they waited for a space. But fees there are only around £20,000 per year so you could do the whole of y9-y13 for not much more than the cost of one year at an SEN specialist.
There are also a few normally academically selective private schools, offering a very challenging curriculum and mostly full of very academically able children without SEN but some do have a few pupils with EHCPs who named that school as the only one that could meet their needs.
Which of these very different kinds of private schools are you talking about for your DC? And whereabouts in the country are you?