At your age I was at school in Australia, but wanted to join the RAF. They wouldn't accept the Oz qualifications I was studying for, so I home/school self-studied (the school were most helpful) to take GCE. I sat the exams with a candidate number of 001; the only person in WA taking them. I failed on two of the five required, but a couple of months at college on returning to UK saw them away. I joined the RAF some two weeks before my 18th birthday, and was awarded wings at 19 1/2. You're young enough to get the qualifications, so get your head into the books. Night school/day release, whatever is available these days. Keep an eye on civil flying too, in case the military is out. Good luck.