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Attending a quality kindergarten that provides experienced teachers and small classes yields measurable benefits, such as higher salaries in adulthood. That finding, in a study led by professor of economics Raj Chetty, has caused a stir by demonstrating that even the earliest school experiences can affect students’ subsequent quality of life, exerting more influence than researchers previously thought.

Chetty and his colleagues, including Harvard Kennedy School associate professor of public policy John Friedman, examined data from Project STAR, a study of nearly 12,000 Tennessee kindergartners conducted in the mid 1980s. The children were randomly assigned to their teachers and to classes that were small (about 15 students) or large (around 24 students) and subsequently tracked (see “The Case for Smaller Classes,” May-June 1999, page 34).

Previous analyses of Project STAR showed that children in small classes, and those with the best teachers, scored higher on standardized tests in the primary grades. But by the time those students reached junior high, the advantage vanished, a phenomenon known as “fade out.” “By the time they’re in seventh or eighth grade, the kids in a better kindergarten class are not doing any better on tests than the kids in not-so-good classes,” Chetty says. Conventional wisdom held that the boost from a good kindergarten ebbed with time. “What’s really surprising about our study,” Chetty says, “is that [the advantage] comes back in adulthood.”

When he and his colleagues looked at what the students—now in their early thirties—recently earned, they found that those who had the best kindergarten teachers make more money. “We estimate that if you move from an average teacher to an excellent teacher, each student gains an average of $1,000 per year in earnings,” Chetty says. “If you add that up over a student’s working life, and adjust for inflation and interest rates, you get a total lifetime gain of around $16,000 per child.” In a classroom with an average of 20 students, then, an excellent teacher means a total gain in earnings of $320,000 for the entire class. And students from small classes experienced other important advantages: they were more likely to attend college, to own a home, and to save for retirement.

What characteristics separated the best teachers from the worst? Chetty says researchers know little about the teachers except that the standouts tended to have worked in schools longer than the least effective teachers.

And how do excellent teachers create these long-term advantages? Chetty suspects the answer lies in so-called “non-cognitive measures.” When the STAR students reached the eighth grade, their teachers evaluated them on attributes such as manners, the ability to focus, and self-discipline. Students who had the best kindergarten teachers excelled at these measures, even in eighth grade. “This is a little speculative, but I think it’s consistent with the evidence: A good kindergarten teacher raises your kindergarten test scores by teaching you skills like how to be a disciplined student,” Chetty says. “Those skills don’t necessarily show up in later academic tests, but they end up having a big pay-off in the long run.”

Chetty and his colleagues are working to publish their results, which have not yet been peer-reviewed. When they first presented the findings last July, at a meeting of the National Bureau of Economic Research, wide publicity followed, including comments from bloggers who doubted the researchers could distinguish the influence of kindergarten from such factors as parental education or income. Chetty responds that their findings are particularly meaningful because the students were literally assigned to their classrooms by coin toss. “There was no way for the richer parents or the more informed parents or the more motivated parents to put their kids in better classes,” he says. Randomization ensured that the composition of classes was comparable, so “any differences across the classes can be attributed to the classes themselves, rather than to potential things like parental background.”

He also disagrees with those who say a gain of $1,000 a year is too small to matter, pointing out that these students earned an average of $16,000 a year at age 27, so $1,000 represents a significant 6 percent raise. Chetty adds that the new study merely highlights the benefits of a single year. It’s likely, he says, that each subsequent year with an excellent educator would yield additional pay increases: “The point is that over the years, that adds up to quite a bit of money.”