In high school, i only did chemistry and physics, and i would rate them from easiest to hardest would be chem first then physics, Although being pretty good at maths, i found physics a little bit harder to grasp, maybe it was due to lack of study and possibly teacher if that's an excuse. teacher was hardly there at all to teach us anything.
Now in uni, and did chem and bio, i would now rate the three as chem being the easiest, the physics then biology. Biology is full of theory, and looking at microscopes, i have bad memory and look at plants, pfft, not my thing.
So now im doing a 2nd year chemistry major, i enjoy it even though most of the time i dont know what the lecturer is on about, but i seem to grasp things quicker if it is related to chemistry. biology is still part of my course unfortunately, and i struggle just reading a sentence let alone a book. and physics, offered at uni, but being horrified at what i got during high school, it'll be far away as possible.