Researchers looking at the impacts of teachers union membership on schools have had an easier time focusing on finance-related outcomes—including former students’ earning power as adults—rather than academic achievement. While not the first research to do so, a new working paper exploits a natural experiment to try and overcome the non-random nature of union membership in order to examine student outcomes more directly.
In 2011, Wisconsin enacted Act 10, which effectively made union membership optional. The legislation also specifically curtailed public-sector unions’ collective bargaining rights and required them to hold annual elections to remain legally certified. Prior to Act 10, over 98 percent of Badger State teachers were union members. After its passage, that eventually dropped below 50 percent and roughly half of the state’s 400 union locals were not re-certified by public school teachers.
Morgan Foy, a researcher from the University of Illinois Urbana-Champaign, uses individual-level data on all public school teachers from the Wisconsin Department of Public Instruction (DPI) from 2006–2022. These include demographic characteristics, schools where they worked, and grades and subjects taught. He also was given access to de-personalized data on all public school students in the state over the same time period. These include demographics, attendance and disciplinary records, and standardized test scores for grades 3–8 and 10. Foy normalized exam scores to keep them consistent in the wake of test changes in various subjects and years of the study. DPI data began linking teachers and their students in 2017, thus Foy is able to create a classroom-level teacher value added measure from that point. Union re-certification election results came from the Wisconsin Employment Relations Commission and teacher survey data regarding union membership came from NCES.
Importantly, the methodology hinges on two timely but unrelated developments. The first is that, while Act 10 eventually affected all of public education, implementation dates varied across districts because changes only kicked in when an active collective bargaining agreement ended and a new one began. The second is that, starting in January 2016, state law required all union dues to be itemized as part of reporting by political action committees. This allowed for precise data on who was and wasn’t a union member, a level of detail that was previously unavailable.
As a preliminary finding, Foy reports that higher-performing teachers, as measured by value added, are less likely to remain union members relative to their lower-performing peers after union decertification, keeping in mind that individual teachers could still opt to be union members even if their local organizations were decertified. Relatedly, he finds no difference in who opts in and who opts out of union membership by value-added score when they have this choice. “This is consistent,” he concludes, “with the idea that lower-performing teachers value the representation benefits that unions provide relatively more than higher-performing teachers.”
Exploiting the staggered decertification process experienced by local teachers’ unions over time, Foy finds positive impacts on student outcomes in districts with less union membership compared to districts with more membership. Specifically, by three years after decertification, student test scores in math, English language arts, science, and social studies increased by over 5 percent of a standard deviation, and student attendance increased by roughly 1 percent (in average days attended) five years after decertification. Additionally, Foy determines that these benefits are not due to changes in the composition of the teaching force following a loss of union representation, as he found no evidence of differences in teacher turnover rates with or without decertification. Rather, his value-added analysis indicates that teachers who were employed both pre- and post-decertification increased their productivity in decertified districts compared to districts whose union membership remained stable.
Foy concludes from his unique analysis that ending “union protections” for teachers results in direct academic and nonacademic benefits for students. Unfortunately, the mechanisms at work are unclear. (It’s definitely not increased teacher pay or more classroom inputs, as the data available indicate neither of these occurred in districts where unions were decertified.) Instead, Foy surmises that “union efforts to insulate workers may adversely affect the quality” of teaching from the start. And only by ending the union representation system will many teachers reach their full productivity and quality.
SOURCE: Morgan Foy, “Selection and Performance in Teachers’ Unions,” NBER Working Paper (October 2025).
