How to Proceed?
Hi DD
Here are some thoughts
1) Make sure you do maths and physics at year 12, as maths is required and physics is very, very useful as background to CPL/ATPL subjects. If you don't do year 12, go to Point 3. (But in any case look to see if high school maths is required by your prospective airline employer).
2) If your ATAR is good enough when finishing year 12, suggest you consider doing a degree in aviation (or science or engineering where you can learn some more technical or aviation management background). A degree will take a little longer but a good degree will give you some back-up later as well as some slight advantage as selection committees will be able to see you have additional capability to absorb information, and are motivated. However, some aviation degrees are only just an excuse to do CPL via fee-help (which is a loan and will cost a lot more in the long run), and some have very poor academic subjects alongside the flying. You don't need a degree to get a job as a pilot (in Australia), but without one if you lose your aviation medical you may find life tough.
3) Whether you do or do not do a degree, be very careful where you do your training; there is a huge range of quality out there (and the airlines know it), as well as a range of costs so be careful of what you sign up for vs what you get. Never pay all your training fees up front; make sure there is a schedule. If you can train full-time then that will be more effective for you; but if you can't then make sure the flying school can meet your needs in terms of instructor availability (schools with cadetship contracts may give preference to the cadets, leaving the private flying students as 2nd priority).
4) Read the fine print about cadetships: they vary greatly in cost, (up-front as well as return of service; repayment schedules etc) and are varied in what you get afterwards in terms of command time and onward job committment. As far as I know no cadetships in Australia guarantee jobs even if your record is spotless! So you will end up paying in one way or another no matter what. Cadetships also stamp their airline logo on your forehead (so to speak), so if you need to apply somewhere else your previous history of affiliation is clear. This may or may not be an advantage.
There is lots of more detailed info on pprune about individual programs and organisations, time spent researching will not be wasted.
good luck
Seabreeze