That is a little bit difficult to estimate for myself. This list is more or less formed by my experiences in the subjects, but as desired it begins with the easiest A-Level and ends with the hardest one:
Biology Chemistry Physics Mathematics (without analysis Physics would be the hardest A-level)
I think people who do physics are those to be looked up to! It's pretty much applied maths, amazing superb stuff!! Keep up the good work guys!! I'm proud of you, as cheesy as it sounds!!