U.S. Census Bureau, Current Population Survey. 2020. “School Enrollment in the United States: 2018,” Table 3. https://www.census.gov/data/tables/2018/demo/school-enrollment/2018-cps.html; Education Commission of the States. 2020. “50-State Comparison: State K-3 Policies.” https://www.ecs.org/kindergarten-policies/.
