Hello Anthony,
The next few years will be tough for airlines in Australia. I doubt there will be any cadetships on offer for some time. It might be a bit different when you finish Yr 12 but don't let flying schools fool you into believing you will get straight into Qlink or REX when you finish.
I did an economics degree instead of an Aviation based one. Aviation degrees aren't very useful outside of the aviation industry. Business, Engineering or Science is much more marketable as a skill.
Take a discovery flight just to make sure you like flying.
Cheers