I'm pretty sure you can look up the curriculum for any year level on one of the official websites and then do khan academy exercises accordingly.
Not exactly, Khan academy is structured for the US curriculum, whereas the Australian math curriculum varies depending on your state (VCE, HSC, etc), course (Methods, Specialist, General), and even school (As schools may choose to approach topics in different orders).
I think your best bet is to find your school's
scope and sequence for your course (should look something like this)
This will tell you what topics and what order you'll be covering content in, which you can then use it self learn on Khan Academy
(eg. "Khan Academy Differentiation of Trigonometric Functions").
This will ensure you're only covering content relevant to your course and narrow down the amount you need to learn. If you can't get access to this, your syllabus is your best bet.
Hope this helps!