Photo: Kate Samp for Strategies for Children

Two Harvard researchers have studied the long-term effects of class size and classroom quality in kindergarten through third grade and find that both produce lasting benefits into adulthood. In an article (“The Long-Term Effects of Early Childhood Education”) in the current issue of Communities & Banking, a quarterly journal of the Federal Reserve Bank of Boston, Raj Chetty and John N. Friedman write that the effects of both small class size and high classroom quality show in higher rates of college attendance, savings, marriage and neighborhood quality.

Chetty and Friedman examined data from Tennessee’s large-scale Project Star. Between 1985 and 1989, about 11,500 children and their teachers were randomly assigned to small, 15-student classrooms or regular 22-student classrooms. Children, by and large, were assigned to the same-sized classes through third grade, with children originally assigned to a smaller class continuing to be assigned to small classes. In fourth grade, all were assigned to regular-sized classrooms. Previous studies, Chetty and Friedman note, found that being in smaller classes and having better teachers led to higher test scores, although the benefits fell somewhat in grades four to eight.

However, when the researchers looked at participants as young adults, ages 25-27, the long-lasting benefits of both class size and classroom quality were striking. (They used classmates’ test scores as a proxy for classroom quality.)

“The larger surprise came from our findings that K-3 classroom quality has a big effect on adult outcomes,” Chetty and Friedman write. “Even though the effect of better classes on standardized test scores quickly faded in later grades, being assigned to a higher-quality classroom was an important predictor of later earnings. Remarkably, we also found substantial improvements on virtually every other measure of success in adulthood that we examined. Students who were randomly assigned to higher-quality classrooms were eventually more likely to attend college, to own a house, to save for retirement, and to live in a better neighborhood.”

(Although class size did not have a statistically significant effect on earnings, Chetty and Friedman wonder if monetary advantages might emerge over time as participants benefit from their higher levels of educational attainment.)

The authors speculate that the lasting effects might be the result of noncognitive benefits, rather than simply academic factors. Students in higher-quality classrooms scored higher on measures of behavior, social skills and classroom participation as well as on standardized tests. “Although the academic gains fade in later grades, the improvements in noncognitive measures persist over time,” they write.

Chetty and Friedman conclude by considering the broader implications of their study.

“These results demonstrate that local financing of schools (and disparities in the ability to hire the best teachers or keep classes small) may contribute substantially to the growth of income inequality in the nation,” they write. “Therefore, tax-policy reforms at the state or especially the federal level that generate more uniform school quality could help substantially.”