As I mentioned in a previous post, most of the random assignment experiments for the effects of preschool have focused on disadvantaged students. In general, foundations and governments have not financed random assignment experiments on how preschool has affected more advantaged students. As I have explored in previous posts, there is evidence of the effects of preschool on more advantaged students from studies that use other rigorous methods, but I have not yet cited a random assignment experiment.
For evaluating the effects of preschool on more advantaged students, the only random assignment experiment that I am aware of looks at the Brigham Young University Preschool Program. This program serves a group with considerable advantages in education and various social measures. Most of the parents are college graduate or above. Over 96% are two-parent families, and most of the mothers are not working, so there is plenty of parental time available for paying attention to children. According to the study authors, “The parents’ educational level, the level of the fathers’ occupation, and the level of family income were all above average for the Mountain States region of the country” (Larsen and Robinson, 1989, p. 136).
Early results from this project found that “social competency…was enhanced through preschool participation …although there were no significant group differences in kindergarten test results”. Later follow-up results as of second and third grade found that “Males who had attended preschool scored significantly higher on the reading vocabulary, total reading, spelling, total language, and total battery components of achievement measures than did males who had not attended preschool.” In contrast, for females, preschool participation had no statistically significant effects on academic achievement in 2nd and 3rd grades. From the paper, it appears that the female preschool participants, compared to the control group of non-participants, did better on nine of the 11 test comparisons, but the differences were not statistically significant. This study is based on a limited sample size, with information reported for 55 males in the preschool group and 35 males in the control group, and for 70 females in the treatment group and 36 females in the control group.
Given these small sample sizes, it takes fairly large preschool effects for such effects to be detected as statistically significant. The mean achievement gains for males on the overall test battery imply a percentile gain in test scores of a little less than 10 percentiles.
Based on Chetty and his colleagues’ results for how 2nd and 3rd grade test scores affect adult earnings, this test score gain for males would be expected to increase average annual adult earnings at ages 25 to 27 by a little over $900 or 5%. (These calculations rely on converting the mean gain in normal curve equivalents to a percentile gain, and then use Chetty et al’s results from column 1 of their Appendix Table 5.)
An increase in annual adult earnings of $900 or 5%, even for only a portion of a full working career, would clearly be sufficient to justify even a very expensive pre-k program. Therefore, based on the BYU study, we can say that there is evidence from a randomized experiment that pre-k can pay off for males from more advantaged backgrounds.