The author employs a regression discontinuity design to provide direct evidence on the effects of grades earned in economics principles classes on the decision to major in economics and finds a differential effect for male and female students. Specifically, for female students, receiving an A for a final grade in the first economics class is associated with a meaningful increase in the probability of majoring in economics, even after controlling for the numerical grade earned in the class. This suggests that for female students, the feedback that is embedded in the course letter grade has an encouragement effect on their decision to study economics further. The author finds no evidence of a similar effect for male students. (Contains 13 notes, 6 tables, and 5 figures.)