$320,000 Kindergarten Teachers: Your Kindergarten Classroom Can Leave a Lasting Impact on Your Earnings and Your Quality of Life Long after Circle Time Is a Distant Memory

Could the quality of your kindergarten experience make a difference in your lifetime earnings? Or whether you're married or own a home? Our study of an experiment that randomly assigned students to different kindergarten classrooms suggests the answers are yes. In our recent National Bureau of Economic Research working paper (Chetty et al. 2010), we present evidence demonstrating the tremendous importance of early education. Improvements in kindergarten test scores translate into higher lifetime earnings and improvements in a variety of other outcomes, ranging from where people live to whether they're married. We estimate that an above-average kindergarten teacher generates about $320,000 more in total earnings than a below-average kindergarten teacher for a class of 20 students. Isolating the impact of quality in the classroom isn't easy. Under normal circumstances, children in better classrooms--that is, classrooms with better teachers, more resources, better-behaved classmates, or other favorable environmental factors--are different in many dimensions. For instance, they may come from wealthier neighborhoods or be better prepared upon kindergarten entry. As a result, students in better classrooms may do better simply because they had advantages to begin with and not because of the class itself. This difficulty plagues most empirical studies in education: How can we separate causation from correlation? We cut this Gordian knot by using data from a randomized experiment, the gold standard of research. In the experiment we studied, students and teachers were randomly assigned to specific classrooms. As a result, there are no systematic differences in background characteristics across the classes, and we can say with confidence that any differences in later outcomes were caused by differences in classrooms. We analyzed data from Project STAR--the largest and most widely studied education intervention conducted in the United States. STAR was a randomized experiment conducted in 79 Tennessee schools from 1985 to 1989. In STAR, some 11,500 students and their teachers were randomly assigned to attend either a small class with an average of 15 students or a regular-sized class with an average of 22 students. In general, students remained in their randomly assigned classes in grades K-3 until the experiment concluded and all students returned to regular-sized classes in 4th grade. Previous work has shown that small classes increased students' standardized test scores by about 5 percentile rank points in grades K-3. And students who had better teachers also scored higher on tests in grades K-3. But the longer-run effects were less impressive: The lasting benefits from small-class attendance fell to 1 to 2 percentile points in grades 4-8, as did the benefits from having a better teacher. However, the end goal of education is not merely to increase test scores. We use test scores because we think they're a good proxy for lifetime outcomes. But no one has ever verified this assumption. The goal of our project was to fill this important gap by linking the STAR data to data on adult outcomes. We find evidence that kindergarten test scores are indeed very good at predicting later outcomes. There is a strong correlation between kindergarten test scores and a wide variety of outcomes in early adulthood (measured between ages 25 and 27). For each 1 percentile point increase in kindergarten test scores, the students' yearly earnings increase by $130-or almost 1% of mean earnings. The relationship diminishes only slightly if we account for family background, for instance, as measured by parental income. Kindergarten test scores also predict a wide variety of other positive outcomes. By age 27, children with higher scores are much more likely to have attended college, have retirement savings, be a homeowner, and live in a better neighborhood. Do test score improvements in early grades improve lifetime outcomes? …