It's pretty clear that you have absolutely no idea about the types of children who have SEN, the breadth of the types of SEN and how it impacts those children, including the support required.
My son's state school basically ignored the fact my son is austistic with sensory requirements (he masks and has selective mutism, so essentially was no bother, despite being hugely affected by being in a normal class). That was until the emotional based school avoidance started and his lack of ability to cope started to affect their stats. So, in order to save their stats, with a byproduct of helping DS, they got the Ed Psych in to assess prior to starting the EHCP process.
Essentially, the upshot is that he's more than capable of a mainstream type of education, but this would be better in small class sizes due to his sensory needs. And there are loads of other bright, capable, autistic kids in the same boat. Our LEA admitted during the EHCP process that these children in our area fall through a gap, as there's no suitable peer group in the local special schools (LEA or private) but mainstream state can't provide the small class sizes these children needs. Other LEAs do have more suitable provision, so I'm not saying this is a problem nationally. It is for us.
These are the types of children who would benefit from state-funded private education (intellectually bright, but sensory processing issues which mean that large classes inhibit learning / ability to attend). Our local private school has a handful of children with EHCPs, where the state is paying their fees. And I will absolutely push for this for DS if our state school compromise doesn't work, when the EHCP is reviewed.