Make sure you complete year 12 not just because its needs but because its something to fall back on if something goes wrong.
For me Year 12 was a fantastic year, you learn so much about yourself, something which is more important than the content IMO, while you mightn't get to apply that much of what you learn in yr12 to aviation what you can apply is the study skills you learn. Prior to year 12 I was a shocker at exams, I was a smart student but put me in an exam and i always seemed to struggle, I focused on this in both year 11 and 12 and 2 years after finishing Year 12 I had passed all CPL, IREX and ATPL exams first go - even flight planning. (and hopefully my first Type rating exams next year haha)
Year 12 is not about knowing how to do complex maths quickly or know random facts about Russian history, its about how you take slabs of information or complex ideas and remember and understand them, something which definitely applies to aviation. As an Instructor i've seen plenty of students who can fly better than I can but give up because they can't pass exams.