I can only speak from my own personal experience but.
I left School in 1997 with 3 good A levels. I decided to go on to University and complete my degree.
I have now left University and am beginning the long road by applying to sponsorships etc and well paid graduate jobs if I have to do it myself.
I now have a full back if I fail a medical. I now have a full back that if after 25 years the aviation industry is now what we know it is to be now.
I wouldn't jump into anything and in all honesty would advise you to work hard and get those A Levels. There are no guarantees in life, and an extra year might seem to be the end of the world right now but don't look back in 20 odd years and say why didn't I do those A levels.
Best of luck in whatever you choose to do
Sagey