Over the years, at least half the states have used mandates or incentives to reduce class sizes, but the reductions are one of the most expensive interventions in education, and lately, some places are backing off the limits.
Wisconsin, for example, is ending its program after two decades to give schools more flexibility in deciding how to improve achievement.
California, which has spent at least $20 billion since 1996 to reduce class sizes, has loosened its restrictions and now has some of the most crowded classrooms in the country with 22.5 pupils per teacher, according to the National Education Association, which notes that K-3 classrooms typically have nine or 10 more students than the student-teacher ratio.
Florida has spent more than $30 billion since 2003 to reduce class sizes, but state lawmakers have repeatedly looked for ways to ease the requirement.
Some argue there are better ways to boost achievement than taking on the expense of hiring more teachers to staff additional classrooms.
"Small classes do provide modest benefits to the students with respect to academic achievement," said Martin West, an associate professor of education at Harvard, "but the benefits are less strong than being assigned to a particularly effective teacher."
Schools Learn Expensive Lesson on Class Size
Many states spent billions to shrink student-teacher ratios but now seek cheaper ways to improve performance
Kindergarten students get to know each other at Westside Elementary on the first day of school for Hernando County, Fla. on Aug. 10. Photo: Brendan Fitterer/Tampa Bay Times/Zuma Press
By Jo Craven McGinty
WSJ, Sept. 30, 2016 10:28 a.m. ET