Sorry, I'm not familiar with the S.A. funding situation. If it is still funded, the following programs at secondary level look interesting:
Ignite Program.
Even if a school doesn't receive extra funding for gifted programs, some schools will be able to cater for gifted children better than others. Things to look out for would be a differentiated curriculum, where children are taught in small groups within their class at their appropriate level or a vertical subject program where children leave their own class and join others from different year levels who are at the same level for that subject. I think the most important thing is that the school has a commitment to meet the needs of gifted children, and isn't simply paying lip service to the idea.
I don't know if you've seen this site -some of the information is a bit old now, but you might find it useful:
http://home.alphalink.com.au/~drednort/schoolsinsa.html
I hope to have an updated list of schools with gifted programs in other states soon (NSW/VIC/WA all had easy to find descriptions for their government schools, the other states are a bit trickier).
Annabel.