I did poorly mainly when I didn't pay attention at all, or something was explained really poorly. Most of the time, studying would serve no purpose to me because I have a semi-photographic memory (being an artist really helps, trust me.), so the information would typically be stored away when I needed it.
Most of the time, bigger projects were what brought me down, just because I'm a super procrastinator.
I'd score average/below average/above average on projects, below average especially if I didn't see the point. A great example was a Trigonometry ESSAY I had to write about how knowing different equations and the like from Trigonometry was important and useful in reality. Too bad we have calculators in today's modern age that automatically calculate these things, and that I had poor teachers for both Geometry and Trig. D:
Oh, and homework was the bane of my existance. That always hurt my grades if I didn't get it done in school. ;D How ironic.