If one Teach For America (TFA) corps member can boost student test scores at a higher rate than other teachers in the same school, would multiple TFA corps members in the same school result in even higher student scores?

New research by Michael Hansen, Ben Backes, Victoria Brady and Zey Xu addresses this question by looking at Miami-Dade County Public Schools, where TFA teachers are purposefully clustered into a targeted set of disadvantaged schools.* This notion — that TFA's impact on high poverty schools could really blossom if more corps members were clustered in a school — is one TFA has suggested in the past.

This study, like those that come before it, finds that TFA corps members pack a lot of punch in mathematics, consistently producing nearly three months' more achievement in mathematics over a single school year than their non-TFA peers. When it comes to reading scores, though, the authors continue to find what other research has found: there isn't much difference.   

So, is their largely positive impact greater than the sum of its parts? In a word, no. The study found no spillover effects on the performance of non-TFA colleagues. Student achievement in math increased only by the amount of each additional TFA teacher and no more. Clustering the corps members had the effect of concentrating these gains in placement schools, but TFA's total impact in the district would have been the same had the corps members been dispersed evenly throughout the district.

*For more information on teacher distribution in Miami-Dade County Public Schools, be sure to read NCTQ's recent paper, Unequal access, unequal results.