The Chicago teacher strike seemed to be heading toward resolution on Thursday, although school probably won’t be back in session until next week. Among the teachers’ complaints was Mayor Rahm Emanuel’s plan to base evaluations largely on student test scores and to expand charter schools that hire non-union teachers. Are unionized teachers better than non-unionized teachers?
It’s not clear. Despite decades of trying, no one has come up with a perfect study design to measure the effects of unionization on teacher performance. One strategy favored by economists is to ask what happens to student outcomes when the teachers in a school district unionize. These studies don’t reflect well on unions. An oft-cited 1996 study found that the high school dropout rate in a school district increases 2.3 percentage points after its teachers unionize. The study also suggested that unionization tends to soak up a district’s financial resources: When non-union districts increase salaries and reduce class size, the dropout rate decreases. In unionized districts, however, the dropout rate is virtually impervious to increased spending. Another studied, published in 2009, was slightly kinder to unions, finding that teacher unionization had no significant impact on the dropout rate.
The problem with these studies is that the high school dropout rate is an imperfect benchmark for teacher performance. It relates only to low-achieving students and says nothing about how teachers are serving the top students who are unlikely to drop out. In addition, students drop out of school for a variety of reasons that have nothing to do with teacher performance, such as chaotic home lives and poverty. Unfortunately, researchers haven’t found an alternative endpoint for these studies. The great wave of teacher unionization occurred in the 1960s and ‘70s. At that time, many school districts didn’t administer standardized exams, and those that did kept poor records of the results. Standardized exam data is now widely available, but few schools are changing their union status these days.
Another strategy is to compare test scores in union and non-union school districts. Teachers unions look much better by this measure—the American Federation of Teachers, the nation’s largest teachers union, likes to point out that states with strong collective bargaining rights, such as Massachusetts, tend to have higher test scores than anti-union states like Texas. But this comparison has serious methodological flaws as well. States and school districts with unions have different demographics than those without unions. Urban school districts, for example, are significantly more likely to be unionized than rural districts. The union-friendly states with high student achievement also have wealthier families. These factors have their own impact on student achievement, independent of whether teachers are unionized. Researchers attempt to control for them, but it’s extremely challenging in the messy reality of student and teacher performance.
Finally, you might look at how the changes unions advocate affect student performance. Labor historians point out that teachers unions improved learning conditions decades ago. The unions fought for climate-controlled classrooms and planning time for teachers to prepare lessons and work collaboratively, all of which benefits students. Today, however, unions resist performance-based incentives for their members. Research has repeatedly shown that rewarding top teachers is a win for students.
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Explainer thanks Michael Lovenheim of Cornell University and Kevin Welner of the University of Colorado at Boulder National Education Policy Center.
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