In a very recent paper, “Teaching Students and Teaching Each Other: The Importance of Peer Learning for Teachers,” authors C. Kirabo Jackson and Elias Bruegmann present a case for peer effects in teacher quality. From the abstract:

Using longitudinal elementary school teacher and student data, we document that students have larger test score gains when their teachers experience improvements in the observable characteristics of their colleagues. Using within-school and within-teacher variation, we further show that a teacher’s students have larger achievement gains in math and reading when she has more effective colleagues (based on estimated value-added from an out-of-sample pre-period). Spillovers are strongest for less-experienced teachers and persist over time, and historical peer quality explains away about twenty percent of the own-teacher effect, results that suggest peer learning.

The findings appeal to our intuitions about the labor market. In manual labor, when high-capacity workers develop new methods to make production more efficient, these “technologies” are soon replicated by the rest of the labor cohort to maximize efficiency. In education, the interaction between teachers allows the “technologies” of teachers with particularly effective techniques to diffuse to lower-quality teachers.

Peer effects have long been studied at the student level: Students appear to benefit from greater heterogeneity of skills in their cohort. For those of us interested in the economics of education, this novel research on peer effects for educators is exciting news. Usually, schools seeking to improve student performance at the margin will employ a cost-based approach that can include: reducing classroom size, increasing teacher pay, or increasing per-student spending and resources. This research provides the basis for a simple qualitative adjustment: school administrators should use the evidence to more carefully match teachers to their positions in order to exploit the full benefits of the heterogeneity of teacher quality.