Nonwhite students at community colleges are more likely to stay in classes and to earn higher grades if they have instructors of their race or ethnicity, according to a study released Monday by the National Bureau for Economic Research. But the same is true for white students, meaning that hiring more minority instructors may result in decreased performance by white students.
The positive impact of having a same-race instructor appears to be the greatest on black students, and on younger students.
The study, "A Community College Instructor Like Me: Race and Ethnicity Interactions in the Classroom," may be controversial, since it touches on several hot-button issues in higher education, including racial gaps in academic performance of students and affirmative action in faculty hiring. Further, the study arrives at a time of intense interest from educators and politicians in finding ways to increase completion rates and the academic performance of community college students. The abstract is available here. 
The study was conducted by three economics professors: Robert Fairlie of the University of California at Santa Cruz, Florian Hoffmann of the University of British Columbia and Philip Oreopoulos of the University of Toronto. Their analysis is based on a large data set (more than 30,000 students in more than 21,000 course sections) provided by De Anza College, a community college in Northern California. The authors write that they believe their research represents the first large-scale study on the impact of instructor race on community college student performance.
De Anza has a diverse student body: Asians make up the largest group (51 percent), followed by white students (28 percent), Latino students (14 percent), black students (4 percent) and other nonwhite students, including Native American and Pacific Islanders (3 percent). White and Asian students are more likely than other groups to finish the courses they start and to earn higher grades.
At De Anza, the instructors are much more likely than the students to be white. Seventy percent are. In many ways, De Anza is typical of many community colleges in having a faculty that is more diverse racially and ethnically than is the case at many elite colleges, but that does not generally match the diversity of the student body. Notably, however, the percentage of black faculty members at the college is slightly higher than the percentage of black students enrolled.
Among all nonwhite groups, the study found a gain of 2.9 percentage points in the proportion of students completing courses taught by instructors of the same race as students -- cutting in half the gaps in minority vs. white course completion rates. (Among all students in all non-recreational courses, 24 percent of white students drop out, compared to 26 percent of Asian students, 28 percent of Latino students, 30 percent of black students and 28 percent of other, nonwhite students.)
Among students who don't drop out, there are also gaps between the performance of white and Asian students and that of other groups, especially black students. For instance, of those students who don't drop out, 89 percent of white and Asian students pass, compared to 82 percent of black students; and 68 percent of white and Asian students who complete courses earn at least a B, while only 53 percent of black students do. For black students taught by a black instructor, there was a gain of 13 percentage points -- among those who completed the course -- in the proportion earning a B or higher.
At the same time, the authors note that there were declines in various performance measures for white students taught by non-white instructors.
The authors write that their findings may leave some wondering whether minority students learn more effectively from minority instructors or whether those minority instructors give better grades to minority students than do white instructors. They rule out discrimination (positive or negative) from the instructors by looking at additional data. First, they note that the dropout rates are constant by race and ethnicity, even before the instructor has handed out the first set of grades -- so these patterns aren't motivated in significant part by hard or lenient grading.
Further, they note that the shift in academic performance by minority students is most evident for younger students (for the purposes of this study, up to 21.5 years old), with hardly any impact on older students. If the students were reacting to discrimination by instructors, the impact should be evident among older students as well, the authors write. The authors write that they suspect younger students "are likely to be susceptible to role-model effects, while older students are not."
Another possible factor is that talented minority students might seek out minority instructors, but the researchers write that there is evidence only for a small impact of "sorting," and that they control for it.
The authors conclude their paper by calling for more research -- and stop short of urging community colleges to hire more minority instructors.
"Our results suggest that the academic achievement gap between white and underrepresented minority college students would decrease by hiring more minority instructors. However, the desirability of this policy is complicated by the finding that students appear to react positively when matched to instructors of a similar race or ethnicity but negatively when not," they write. "Hiring more instructors of one type may also lead to greater student sorting and changes to classroom composition, which may also impact academic achievement. A more detailed understanding of heterogeneous effects from instructor assignment, therefore, is needed before drawing recommendations for improving overall outcomes. The topic is ripe for further research."