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The best teachers tend to leave when their schools experience an influx of African-American students, according to a study of the Charlotte-Mecklenburg, N.C., school district.
C. Kirabo Jackson, an associate professor of labor economics at Cornell University, in Ithaca, N.Y., studied patterns of teacher movement in Charlotte-Mecklenburg schools between 2002 and 2003, which was when the 137,000-student district ended its long-running policy of busing students to keep schools racially integrated. His results, published last month in the Journal of Labor Economics, show that, at all levels of schooling, high-quality teachers—both black and white—were more likely to switch schools as the policy change began to take effect and student populations shifted.
“I’m not showing that teachers don’t like black students,” Mr. Jackson said. “I’m showing that, when you substantially change the makeup of the student population, teachers react in this way.”
A growing body of research has found that students in schools with high concentrations of poor students and students from minority groups tend to have teachers who are considered, on average, to be of lower quality than teachers in better-off suburban schools. And a handful of studies also suggests that, in states such as New York and Texas, teachers have tended to move from those disadvantaged schools to more affluent ones.
According to Mr. Jackson, it’s been hard to home in on the reasons for those teacher-migration patterns. For instance, were teachers moving to schools out of convenience, so that they could be closer to their own homes, or for higher salaries, or because they were drawn to certain types of students, such as high achievers or students from white or wealthy families?
Mr. Jackson said his study offers a better handle on those questions because he was able to track the changes that occurred before and after the busing policy ended and correlate teachers’ movement to changes in student demographics. When the policy changed, the racial makeup of some schools changed suddenly, yet the neighborhoods surrounding those schools essentially remained the same.
The researcher measured teacher quality in three ways: years of experience, scores on licensure exams, and teachers’ “value added” scores, showing how much their students’ achievement scores improved over the course of a school year.
Patterns More Nuanced
His findings don’t suggest that Charlotte-Mecklenburg teachers were flocking, across the board, to the whiter schools. Even though the best of them were leaving, African-American teachers, overall, were more likely to stay in the schools experiencing a large inflow of black students. Likewise, the average white teacher in those schools was no more or less likely to leave as black students migrated in.
“It’s just a difference in the type of teacher leaving,” Mr. Jackson said. “There are teachers who have preferences for low-income, ethnic-minority students and others who do not. They are simply kind of re-sorting themselves.”
He calculated that, for the average school with a student population that is 60 percent black, a 15 percent increase in the number of African-American students translates to a .3 standard-deviation drop in teacher quality. That effect is about the same size, he said, as the boost in achievement that students might get from reducing a class of 23 students by two to three students, or from having a more experienced teacher vs. a novice. He said it could also explain between 3.3 percent and 7.5 percent of the achievement gap between black students and their higher-performing white peers in the district.
“An important implication of these findings is that policymakers should be cautious when advocating policies such as vouchers, school choice, district consolidation, or school busing that require the reshuffling of students across schools,” the study concludes, because the resulting shifts in student population might also lead to shifts in the quality of teachers.
Whether the teacher-movement patterns in Charlotte-Mecklenburg would be typical of other large, urban school systems is unclear.
In studies looking at teacher mobility in Texas, Eric Hanushek, a senior education fellow at Stanford University’s Hoover Institution, found that teachers tended to move to whiter, higher-achieving schools as their careers progressed, but that the teachers who moved were not necessarily the best in their schools, as measured by their value-added scores.
