Difficulty of pre-med compared to high school?

I was wondering how hard is premed courses compared to high school courses. I took some honors and AP's including AP Biology and AP Psychology (and some other history AP's) but not AP Chem or AP Physics. In high school, I got a 3.5 GPA but sadly a 26/36 on the ACT (tbh I didn't study for it). I know it's not the best, and even though I did usually study, I didn't give it my 100%. I would always procrastinate, not pay attention in class, and came home trying to self study for tests but ended... Difficulty of pre-med compared to high school?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums