As a school-leaver, or someone of school-leaving age, you have absolutely nothing with which to impress an employer other than exam results. Several airlines reinforce this point by demanding A-level passes of young applicants who have little flying experience. For those two reasons alone, you should not give up your A-level studies. The days of the airline pilot who left school at 16 with a couple of ropey GCSEs are long gone.
The argument is less clear cut when talking about degrees, but that subject has been done to death here and you can find some of the discussions in the Archive Reference Thread at the top of the forum.
A-levels are important. Don't give them up.
Scroggs