Teachers’ Unions Improve Student Achievement: Insights from California Charter Schools

Over the past several decades, public sector unionization rates have held fairly steady, even as private sector unionization rates have plummeted. Among economists and social scientists, a debate persists as to whether public sector unions serve the public interest. Proponents argue that these unions increase the efficiency of the public sector by attracting more productive workers, while critics contend that public sector unions negotiate wages that make public services overly expensive. In education, critics further allege that teachers’ unions harm children by putting the financial interests of teachers—and of the unions themselves—above the educational interests of students.

Until recently, researchers struggled to evaluate this claim in a rigorous way due to a lack of available data. Most public school teachers unionized in the 1960s and 1970s, before education departments began keeping reliable data on student achievement. As a result, it was difficult to compare the educational outcomes of students in public schools with and without teachers’ unions, holding other factors constant. Previous studies that attempted to evaluate the effects of teachers’ unions on student achievement yielded mixed results.

However, in a new study, Jordan Matsudaira and Richard Patterson capitalized on a recent unionization trend within California charter schools in order to more rigorously assess the relationship between teachers’ unions and performance. Using data from the California Public Employment Relations Board (PERB) and Public Records Requests (PRR) issued to charter schools, Matsudaira and Patterson begin with the findings that about one quarter of charter schools in California became unionized between 2003 and 2013, and that about one third of students in California charter schools are now taught by a teacher who belongs to a union. These findings contradict previous studies which estimated the presence of unions in California charter schools to be much lower, around 12-15 percent.

Next, using data from California Standards Tests (CST) administered between 2003 and 2013 by the California Department of Education, Matsudaira and Patterson analyzed charter students’ Math and English Language Arts scores. The researchers compared the performance of students at 247 unionized California charter schools for which robust CST data was available. They focused their analysis on the 46 schools that not only had complete data, but also had experienced a change in union status over the lifetime of their charters. These schools, which the researchers term “switchers,” enabled the authors to compare student achievement under both union and non-union conditions, holding other factors constant.

Using a difference-in-differences identification strategy, which compares the gains made by schools that chose to unionize compared to those that did not, Matsudaira and Patterson find that teachers’ unions appear to increase student performance in math, but have little effect on student performance in English. Specifically, they find that unions in California charter schools have a positive impact on math scores of about .17 standard deviations, which is statistically significant, and a positive impact on English scores of about .06 standard deviations, which is not statistically significant.

Some of Matsudaira and Patterson’s results stand in opposition to previous research conducted on the effects of teachers’ unions on student achievement. For instance, some earlier studies suggested that unions may produce positive effects only among average students, while harming both high- and low-achieving students. In contrast, the authors of this study find that the positive effects of unions are more pronounced among low-performing students.

Matsudaira and Patterson also identify limitations of their results. First, they find that unions in larger school districts provide less of a boost to students’ test scores than unions in smaller school districts. This reinforces a theory put forth by previous researchers that powerful unions in large districts may have an adverse effect on student achievement by making it difficult for parents to advocate for their children. Matsudaira and Patterson also note that the effects of unions may differ across various contexts, for instance, by the degree of competition the school faces, the flexibility of the school’s contract provisions, or the organizational structure of the school. While the specific behaviors of unions that affect student achievement remain uncertain, Matsudaira and Patterson recommend that further research be conducted in order to better understand the underlying mechanisms by which unions impact school operating procedures and student performance.

Article source: Matsudaira, Jordan D., and Richard W. Patterson. “Teachers’ unions and school performance: Evidence from California charter schools.” Economics of Education Review. 61 (2017): 35-50.

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