What would be the minimum mark to gain a 90% percentile at AS? Say for instance a subject is marked out of 130, and 87/130 is the minimum mark for an A grade and 78/130 is minimum for a B grade. That shows that the 10% between the B (70) and A (80) percentile grades is a difference of 9 marks. But what is the "upper band" for the 90% percentile? Would it be that the difference between A and B grades is 9 marks hence to gain a 90% percentile one would need 87+9=96 marks and hence to gain 100% percentile you would need 96+9 = 106/130 marks?