It's not hard at all to be invited to at least the first interview stage. I think they just take anybody in who shows on the application that they at least know some English (there are two short essay questions, 250 words each).
Since you aren't taking physics, maybe you might want to show them that you're committed to learning this sort of stuff despite not doing it in school. Read up on aerodynamics and the principles of flight – you'll find a lot about this stuff in the first few chapters of any introductory PPL textbook. (The FAA's own is a good start and is
available free on-line)
There's someone here who applied at 17, got accepted when he turned 18, and is now training in Adelaide. However, I don't remember exactly who that is. Search around for his posts.