jakB- Treehouse is a bit of a one of a kind (not quite- there are other like the rainbow school) but AFAIK (in the absence of Prof Davrois as she will correct me) it is entirely based on ABA - so each child has their own programme, and there is a lot of home-school links within programmes. I think each child has a one to one.
LEA's will NEVER set up a school in treehouse style though as it is hugely expensive. AFAIK Treehouse, rainbow, any others have been set up by parents- then the LEAs fight not to fund places there
You have to watch out for LEA's being overkeen on TEACHH- they love it (nice and cheap). In reality though I have found that although LEA's bleat on about TEACHH at the coal face experienced teachers only use it in a limited fashion. Certainly although my son's school don't uses ABA as such- their approach is behavioural in the main. And they use a lot of Pyramid type lesson plans which of course are mainly ABA.
I don;t think there's anything wrong with using a mix of appproaches (whereas in the past I would have wanted purely ABA) providing the approaches are being fitted around the child, rather than the other way around.
Decent sensory work by the way requires facilities. DS1's hydro pool is also a snoezlen room- then they have the sensory room and the dark rooom, and the sand and splash room. Along with lots of outside play equipment. About the only thing they don;t have a tramplines (too big) but they do have people who come in to doo rebound therapy and they have a circus skills group.
Visits are good from outside facilities- for example donkeys come regularly to ds1's school.
The biggest differrence in ds1 since changing provision was demonstrated well today. last aquarium visit with mainstream he refused to go in and I had to collect him. Today he came home saying aquarium and fiish