Iowa School Districts Were More Likely To Adopt COVID-19 Mask Mandates Where Teachers Were Unionized.

During the COVID-19 pandemic, safely reopening schools has been one of the most pressing public health challenges in the United States. At the beginning of the 2020-21 school year, the Centers for Disease Control and Prevention strongly encouraged schools to require mask wearing. Although teachers unions frequently supported such policies, the adoption of mask mandates was uneven. We examined whether teachers unions were associated with mask mandates, using proprietary data on school district-level unionization and mask mandates from the Iowa State Education Association, the state's main teachers union. We found that a 1-standard-deviation increase in the teachers' unionization rate was associated with a 12.5 percent relative increase in the probability that a school district adopted a mask mandate. These findings, which are robust to multiple specification checks, help illuminate an important mechanism by which labor unions have informed safety policies in schools during the COVID-19 pandemic.