We determine how much observed student performance in microeconomics principles can be attributed, inferentially, to three kinds of student academic "productivity," the instructor, demographics, and unmeasurables. The empirical approach utilizes an ordered probit model that relates student performance in micro to grades in prior coursework, demographic information, instructor characteristics, and SAT scores. The micro grade is somewhat informative about general productivity but conveys little information about the most refined type of academic productivity or instructor grading standards, although there is great variation in the average grades given by different instructors. Because of a large unpredictable component of grade determination, however, differences in micro performance across individuals are mostly attributable to non-productivity related factors. As a result, it is very difficult to improve the information individual grades provide about student productivity. Averages of several grades, however, can provide useful information about the productivity of students and the effectiveness of instructors.