For two decades the promoters of public school accountability have been preaching a doctrine that demands better outcomes as measured in students’ test scores.  These accountability hawks leave any consideration of resource inputs out of the conversation and profess that an excellent teacher can raise achievement by holding higher expectations in spite of adverse circumstances.

In a short, readable brief from the National Education Policy Center, The Effectiveness of Class Size Reduction, William Mathis summarizes decades’ of research on class size to demonstrate the truth of what parents intuitively know: small classes help children.  Mathis reminds us that the school “reformers” who have pretended class size doesn’t matter may have found such an argument convenient because hiring enough teachers to staff very small classes is expensive: “Teacher pay and benefits are the largest single school expenditure, representing 80% of the nation’s school budgets.  Thus, small class size is a costly, important, contentious and perennial issue.”  Mathis rejects the conclusions of Erik Hanushek of the Hoover Institution, the primary critic of reducing class size, who claimed—in a meta-analysis of the research literature—that class size reduction is ineffective for improving students’ achievement. Hanushek’s analysis, explains Mathis, has been widely “criticized on methodological grounds in that he gave more weight to studies that showed no impact from lowering class size, while also treating weak studies as equivalent to those that were experimental and/or of much higher quality.”

Mathis summarizes the research that endorses class-size reduction, including the findings of Glass and Smith in 1979 that, “Once the class size fell below about 15, learning increased progressively as class size became smaller.”  He summarizes the Tennessee STAR (Student/Teacher Achievement Ratio) study in which, “Students in Kindergarten in the same schools were randomly assigned to classes of 13-15; to classes of 22-25 with a teacher’s aide; or to classes of 25 without a teacher’s aide…. The smaller classes performed substantially better by the end of second grade in test scores, grades, and fewer disciplinary referrals. The gains lasted. The students that had been assigned to smaller classes were more likely to graduate in four years, more likely to go to college….  The positive effect was twice as large for poor and minority students, and thus narrowed the achievement gap.”  He cites Alex Molnar’s evaluation of Wisconsin’s SAGE (Student Achievement Guarantee in Education) experiment: Molnar and his colleagues concluded that the SAGE project “reproduced the STAR results.”

Mathis cites research by Princeton economist Alan Krueger, who “concluded that class size reduction had economic benefits that outweighed the costs, and even within the large cohort of 22-25 students, the smaller the class, the better the student outcomes… Krueger noted, as have many others, that class size reduction most benefits minority and disadvantaged students, and would be expected to narrow the racial achievement gap by about one-third.  He also estimated that the economic gains of smaller classes in the early grades outweighed the costs two to one.”  Finally Mathis cites recent research by Kirabo Jackson and colleagues at Northwestern University who tracked the infusion of new money after statewide school finance reforms between 1970-2010 and discovered: “A 10% increase in per-pupil spending each year for all 12 years of public school leads to 0.27 more completed years of education, 7.25 percent higher wages, and a 3.67 percentage point reduction in the annual incidence of adult poverty.’  They concluded that the gains were achieved primarily by lower student-to-teacher ratios, increases in teacher salaries, and longer school years.  Gains were strongest for economically disadvantaged children….”

Mathis adds that class size reduction improves schooling in many ways, not merely by raising test scores: “Many of these studies also show improvements in student engagement, lower drop-out rates and better non-cognitive skills… (C)ollege attendance, graduation rate, student engagement, persistence and self-esteem (are) reported as higher.  The gains in test scores are attributed to the greater individualization of instruction, better classroom control, and, thus, better climate.  Teachers have more time for individual interactions with children, consulting with parents, and giving greater attention to grading papers.”

“The payoff from class-size reduction is greater for low-income and minority children.” Mathis concludes. ” Conversely, increases in class size are likely to be especially harmful to these populations—who are already more likely to be subjected to large classes. While lowering class size has a demonstrable cost…. money saved today by increasing class sizes will likely result in additional substantial social and educational costs in the future.”

Currently children in the wealthiest school districts are far more likely to spend their school days in small classes. It is time our society closes opportunity gaps by providing small classes for all children.