It's irrelevant that you go to a good school. It's somewhat irrelevant that you're in the top 10% of your cohort in Year 9. Keep up the good work though.
Specialist Maths is manageable like any other VCE subject.
Year 12 2015: You might (emphasis on the might) be lucky enough to be in the first year of Year 12 Australian Curriculum study designs (if things turn out well AC-wise anyway).
Don't worry about year 12 too much for now and go busy yourself with interesting things.
Have a look at those maths competitions and all that other stuff, might be a good challenge for you.
Work outside of your year 9 content by all means, but go read stuff that interests you, don't restrain yourself to the, pretty restrictive, year 12 study designs already. There's a lot of interesting stuff that's not covered. You wouldn't be doing yourself any favours.
It's good that you have an idea of what you might want to do, but I wouldn't settle and narrow yourself down too early. Be open to change.