The lottery created a natural experiment, allowing the researchers to track the educational outcomes of two otherwise similar groups of students when one group attended preschool while the other did not. In decades of research on preschool programs, this approach has rarely been applied.
The result: among students of similar backgrounds, those who did attend preschool were 8.3 percentage points more likely to enroll in college right after high school. There was also a 5.4-percentage-point increase in college attendance at any time.
“It’s a pretty large effect,” says Pathak. “It’s fairly rare to find school-based interventions that have effects of this magnitude.”
The study did not find a connection between preschool and higher scores on Massachusetts’s standardized tests. But it did find that children who attended had fewer behavioral issues later on, including fewer suspensions, less absenteeism, and fewer legal-system problems.
Indeed, the study’s findings suggest that beyond academic benefits, preschool-goers may learn behavioral habits that keep them out of trouble. “If I had to speculate what’s behind these long-term effects for college, this is our leading hypothesis,” says Pathak.
“There are probably two broader lessons,” he says. “We cannot judge the effectiveness of early-childhood interventions by just looking at short-run outcomes, stopping by third grade. You’d get a totally misleading picture of Boston’s program if you did that. The second is that I think it’s really critical to measure outcomes beyond test scores