Skyrunner61 is correct, and the grades you get at A Level determine what university and courses you can do. GCSE's now I believe are graded from 9-1 instead of A*-U. I believe a C at GCSE is a pass, and most people try to get at least 5 passes. At GCSE, most students study between 8-11 subjects, whilst at A Level you study 3-4 subjects in much greater detail.