rform on a standardized test of any kind: how we feel physically or psychologically that day, whether we have a reading disability like dyslexia or can't hear all that well--even how tired we may be from studying the previous night.
Gould, S. J. (1981). The Mismeasure of Man. New York: W. W. Norton.
What counts for you as a student--and what results in good grades--are how hard you work on your studies and how seriously you take your education. As you've pro