From a very interesting forthcoming paper in the American Economic Journal titled "Partisan Grading" by economists Talia Bar (Cornell) and Asaf Zussman (Hebrew University):
Abstract: We study grading outcomes associated with professors in an elite U.S. university who were identified using voter registration records as either Republicans or Democrats. The evidence suggests that student grades are linked to the political orientation of professors: relative to their Democratic colleagues, Republican professors are associated with a less egalitarian distribution of grades and with lower grades awarded to Black students relative to Whites.
Dataset: 59,874 grade observations from 17,062 students taking 3,277 undergraduate level courses with 417 Republican and Democratic professors.
Results: The variance of grades is higher in courses taught by Republicans than in courses taught by Democrats. Moreover, in additional analysis we find that relative to their Democratic colleagues, Republican professors tend to assign more very low and very high grades: the share of the lowest grades (F, D-, D, D+, and C-) out of the total is 6.2 percent in courses taught by Republican professors and only 4.0 percent in courses taught by Democratic professors; the share of the highest grade (A+) out the total is 8.0 percent in courses taught by Republican professors and only 3.5 percent in courses taught by Democratic professors. Both differences are highly statistically significant. These suggestive results are consistent with our grading egalitarianism hypothesis.
A different illustration of the relationship between political identification and grading egalitarianism is contained in the chart above. The figure displays mean grades by student SAT score ranges in courses taught by Republican and Democratic professors. The observed pattern is consistent with the hypothesis that Republican professors are associated with a steeper slope of the grade-ability profile, i.e. with higher returns to student ability.
Conclusion: We found that relative to their Democratic colleagues, Republican professors are associated with a less egalitarian distribution of grades and with lower grades awarded to Black students relative to Whites.
Professors control the allocation of grades which serve as the primary currency of academia. Our results suggest that the allocation of grades is associated with the worldview or ideology of professors. This finding may inform the public debate on potential reforms to university grading practices. To the extent that the application of objective standards is an important university goal, policy makers should consider limiting the discretion professors enjoy when it comes to grading and making it more difficult for them to use student characteristics as factors in the grading process.
MP: One conclusion here might be that highly motivated, high-achieving students should prefer classes from Republican professors because it's more likely they'll be rewarded with a really high grade (A or A+), and less motivated, lower-achieving students should prefer classes from Democratic professors, because it's less likely that they'll receive a really low grade.
Thanks to Norman Berger.