My DS's SS (that was a 2 -6 development and assessment school) had its own forest school with its own waterproof boilersuits, 2 OTs on site, (one a sensory specialist) 2 SALTs, both Hanen trainers. They took the DC swimming, to RDA, and even on a 4 night residential once a year. It had a well stocked welcoming parents' room, did parenting courses, SHARE courses (teaching us how to help our DC learn through play,) with a free crèche for siblings or DC who attended a different session led by the class teachers, sometimes the SALT or OT and even the EP occasionally.
Parents were actively encouraged to attend sessions at least weekly to share good practice, whenever you wanted at which siblings were welcomed. It facilitated my DS's GFCF diet. It had showers for when the DC needed them, often after Forest school.
It had its own playground with swings, slides, playhouse, working traffic lights, trikes and a separate sandy 'beach' area, a sensory garden and a wildlife area. Most of these built and paid for by the local Zurich employees charity.
While my DS was there the LA tried hard to close it as it was understandably expensive and the LA tried to kill it by refusing to refer DC there and saying there was no demand. Class sizes were about 10 DC to one teacher and 2 qualified SEN LSWs. The national school adjudicator refused to allow it to be closed and even the Ofsted inspector wrote to the adjudicator in its defence, which nearly cost him his job. (Ofsted inspector came back at Christmas to play Santa!)
My DS2 made so much progress there, although it wasn't ABA or even ASD specialist, it had DC with CP and Down syndrome etc as well as ASD. He spent 2 years there and went on to MS school. I was so sad to say goodbye to it and endure a normal 'adequate' MS primary.
And it wasn't perfect. It could have been better. Some of its methods were too child led which didn't always suit those with ASD and could pander to their stims and obsessions. They tried new approaches and methods, were very progressive and would change what didn't seem to be working but this would take time.
But I learnt a lot of my SEN and SN knowledge there, it's why I felt so at home here on MNSN, I think. For such young DC it was almost perfect. My DS did outgrow it and needed to move on, so I still need that perfect primary or secondary.