I assume you're Year 12 next year and have just finished/finishing Year 11?
Anyway, yes, stay in School.
Financially, I can understand the temptation to start working and saving for your qualifications, but honestly, I'm yet to see anyone "better off" by doing so. In New Zealand, we went through this a few years back. Air NZ added University entrance to their minimum education requirements and suddenly Q300 Captains were having to sit High School equivalency exams if they wanted to progress onto Jets. I'm not sure about in Australia, but fortunately there were no specific subject requirements, they merely suggest Maths/Physics/English as they are relevant to Aviation.
In the modern world, dropping out of School to pay for flying lessons will not come across as a "passion for Aviation", instead it will show a "lack of commitment" or "difficulty in learning"... perhaps even a "problem with authority". I suggest you do some research on these forums about modern day Airline interviews, there's plenty of threads from multiple Airlines. Very little of it has anything to do with your flying ability outside of the Sim ride. There's a lot of online testing, problem solving, math reasoning, HR questions etc... I'm not saying you'll learn much along those lines in School, but certainly more than you will if you drop out. If nothing else, School should help you to think for yourself, analyze information and make decisions. When I left School (20 years ago), forms 3-5 (Years 9-11) were almost gap years. The bulk of my learning was in Forms 6&7 (Years 12&13 in NZ).
A PPL is relatively easy to accomplish. If your family is willing to pay, then I'd suggest doing it while finishing School. A number of years ago I took a kid from start to finish in about 6-8 weeks over the Summer Holidays. Mum & Dad were paying of course, and he'd done all the exams earlier in the year so the only limitation was Aircraft availability! He became part of the Furniture at the Aeroclub, any cancellations and he was there to grab the booking.... if I recall, I believe we even gave him a few free hours for washing planes.