Hi Catherine,
As a mother of a child with Autism (primary aged) I have been looking into this subject a lot, but only in my local area. I currently live NOR in Butler, which is up near Quinns Rocks and Mindarie. Butler College opened up a few years ago and they have apparently got a fantastic special needs stream that is integrated with mainstream. The school is HUGE and is still expanding in size and it even boasts an indoor swimming pool. Although your son doesn't need the special needs stream it is certainly a good indication of the school's willingness to understand and work with kids/young adults who require a bit of extra help (or simply understanding).
The Butler College has become so popular because of it's strict uniform policy and high expectation of student attitude and respect that it's become (unfortunately) impossible for anyone outside of the catchment area to gain admittance to the school. So strict is this policy that they require at least three utility bills with your name on them, bills that show you (not your mum, friend or a tenant of yours) actually reside in Butler, so an electricity bill, phone bill and lease (if you rent). The school also require that every student own an Apple Macbook laptop computer (a good $1600+ each) and the uniforms are apparently quite expensive, as are the text books the computers are supposed to replace and there is still the $300 "voluntary" payment per student. It is an Independent Public School, which means they are government funded but have control over their staffing and budget (for the most part) as well as other things.
I've heard good things about the school from parents and the teenagers I've spoken to that attend there all seem to like going there, albeit in their compulsory uniform with school emblem embroidered socks and compulsory black shoes...!
Good luck with your search, and if you end up living up this way you should probably consider Butler College.