How Teacher Turnover Harms Student Achievement

By Andrew Saraf

What happens when teachers drop out? Conventional wisdom has long said that the costs associated with such transitions (e.g., the loss of routine and the loss of an experienced teacher) harm student achievement. Yet the leading research on this topic concludes otherwise: In 2010, Eric Hanushek and Steven Rivkin revealed that teachers leaving schools tend to be less productive than those who stay, suggesting that turnover may in fact be beneficial. This brand-new study from Stanford’s Susanna Loeb and colleagues restarts this debate—and sides with conventional wisdom. Drawing data from 850,000 NYC fourth and fifth graders during the 2000s, the analysts found that within schools, pupils in grades and years with higher teacher-turnover rates scored lower in both English language arts and math, even after controlling for a number of student characteristics—including achievement—and a host of other teacher, school, and classroom variables. Though the drop in achievement is modest, the effect was more pronounced in both lower-performing schools and those with more African American students. What’s more, it was not confined to students of exiting teachers: Indeed, “bystander” students experienced the largest drop in performance, as opposed to those whose teachers left or who were new to the school. (Rebutting Hanushek’s and Rivkin’s original work, the authors find mixed effects on students of “leaver” teachers—likely because, while teachers who leave may perform worse than those who don’t, their successors are not guaranteed to be any better.) This impressively detailed study adds fuel to a long smoldering debate, though Loeb et al. disappoint on the policy front, proposing only greater efforts to keep teachers in schools—without a very convincing prescription for how this might be done