Remember your report cards, if you really had one, in your high school. Were your grades good, bad or FLAWLESS?
My grades ... they would be exceptionally good/high and, sometimes, exceptionally bad/low, swinging back and forth, just like a rollercoaster. Most of the times, I'd be an average student with my 8's, 7.5's, 9's (probably, the Northern equivalent of B-,B and A- ??) but, sometimes, I'd finish the trimester with lots of 10! (once, I managed to achieve six "tens" out of 9, which was crazy)