Agree.
My two half brothers are a case in point, the older one, has high functioning autism coupled with ADHD, his behavioral problems meant that he was put in a special school relatively early, as the mainstream primary school he was in realised they couldn't handle him. Since he went into the special school, has grades dramatically improved and is finding his own niche within mathematics.
My younger brother also has autism but is at the lower end of the spectrum, Unlike his older brother he doesn't have any behavioral problems, is more creatively minded. Being creative alone has put him at a disadvantage within mainstream Primary education, as of recent years they tend to focus on Maths and English, rather than arts based stuff. Anyway the school had tried their best to retain him, we think for funding reasons, despite the fact being in year 6 (age 10) now, his work is of a similar standard to children in year 2 (age 6 - 7 I think), and he hasn't really progressed since then. We felt contrary, to the schools opinion that he would do better in a special school.
Although thankfully in September he's due to start in a special school from year 7 onwards. My hope is that they focus on his creative skills, his previous schools emphasis on logical skills, has made him feel very left behind and he's lost any interest in learning. I hope he regains his interest in learning, otherwise this could affect him for life.
To be honest the way mainstream schools chews up and spits out many autistics is disgusting.
PDA I've never heard of that before, is there any strategies of encouraging the child to do tasks that have been set. IE making the child think they're doing the task on their terms. Apologies if I've grossly misunderstood what PDA is.