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Students in small classes also exhibit statistically significant improvements on a summary index of the other outcomes we examine (home ownership, 401(k) savings, mobility rates, percent college graduate in ZIP code, and marital status). We do not find significant differences in earnings at age 27 between students who were in small and large classes, although these earnings impacts are imprecisely estimated. We find that students assigned to small classes are 1.8 percentage points more likely to be enrolled in college at age 20, a significant improvement relative to the mean college attendance rate of 26.4% at age 20 in the sample. We analyze the impacts of class size using the same intent-to-treat specifications as Krueger (1999), who sHoweverd that students in small classes scored higher on standardized tests. First, we study the impacts of observable classroom characteristics. Our analysis of the experimental impacts combines two empirical strategies. These strong correlations motivate the main question of the article: do classroom environments that raise test scores-such as smaller classes and better teachers-cause analogous improvements in adult outcomes?
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Several other adult outcomes-such as college attendance rates, quality of college attended, home ownership, and 401(k) savings-are also all highly correlated with kindergarten test scores. A 1 percentile increase in end-of-kindergarten (KG) test scores is associated with a $132 increase in wage earnings at age 27 in the raw data, and a $94 increase after controlling for parental characteristics. We begin by documenting the strong correlation between kindergarten test scores and adult outcomes. 1 We use these data to analyze the impacts of STAR on outcomes ranging from college attendance and earnings to retirement savings, home ownership, and marriage. We link the original STAR data to administrative data from tax returns, allowing us to follow 95% of the STAR participants into adulthood. Whether these gains in achievement on standardized tests translate into improvements in adult outcomes such as earnings remains an open question. Numerous studies have used the STAR experiment to show that class size, teacher quality, and peers have significant causal impacts on test scores (see Schanzenbach 2006 for a review). The experiment was implemented across 79 schools in Tennessee from 1985 to 1989. Some students were assigned to small classes (15 students on average) in grades K–3, and others were assigned to large classes (22 students on average). The Student/Teacher Achievement Ratio (STAR) experiment randomly assigned one cohort of 11,571 students and their teachers to different classrooms within their schools in grades K–3. This article analyzes the long-term impacts of Project STAR, one of the most widely studied education experiments in the United States. What are the long-term impacts of early childhood education? Evidence on this important policy question remains scarce because of a lack of data linking childhood education and outcomes in adulthood. Finally, the effects of class quality fade out on test scores in later grades, but gains in noncognitive measures persist. Students who were randomly assigned to higher quality classrooms in grades K–3-as measured by classmates' end-of-class test scores-have higher earnings, college attendance rates, and other outcomes. Third, an analysis of variance reveals significant classroom effects on earnings. Second, students who had a more experienced teacher in kindergarten have higher earnings. Class size does not have a significant effect on earnings at age 27, but this effect is imprecisely estimated. First, students in small classes are significantly more likely to attend college and exhibit improvements on other outcomes. We then document four sets of experimental impacts. We first demonstrate that kindergarten test scores are highly correlated with outcomes such as earnings at age 27, college attendance, home ownership, and retirement savings. This article evaluates the long-term impacts of STAR by linking the experimental data to administrative records. In Project STAR, 11,571 students in Tennessee and their teachers were randomly assigned to classrooms within their schools from kindergarten to third grade.