A recent study of Boston’s universal pre-K program provides additional evidence that pre-K programs have benefits greater than costs for children from middle-class families. This supplements the more extensive evidence that pre-K has high benefit-cost ratios for children from low-income families. This Boston study is by Christina Weiland and Hirokazu Yoshikawa.

Previous research on Tulsa’s universal pre-K program, by me and Bill Gormley and Shirley Adelstein, showed large benefits for both low-income and middle-class families. Test score gains due to pre-K at kindergarten entrance for children ineligible for a free or reduced price lunch were only 10-11% less than test score gains for children whose family income was low enough to qualify for lunch subsidies.

The Boston study estimates similar results. As reported in Weiland and Yoshikawa’s published paper, for most student outcomes at kindergarten entrance, the estimated effects of pre-K did not differ significantly with student eligibility for lunch subsidies.

Christina Weiland graciously responded to an email and sent me an unpublished appendix with subgroup results. From Chetty et al.’s research, we have estimates of the relationship between cognitive outcomes in kindergarten, measured as percentile test score gains, and dollar gains in adult earnings. I used the appendix provided by Weiland to compute the percentile test score gains for children eligible for a subsidized lunch, versus higher-income children who were ineligible for a subsidized lunch. (These are test score effects on four tests, which included vocabulary, letter-word identification, and two math tests.)

I compute, based on Weiland and Yoshikawa’s estimates, that Boston’s pre-K program’s effects on cognitive skills for middle-class children are 29% less than effects for lower-income children.  Percentile gains for children eligible for a subsidized lunch average 21 percentiles across these four tests.  For children whose family’s income was too high to quality for lunch subsidies, the estimated test score gain is lower but still sizable at 15 percentiles.

(Note on calculations: I used the appendix information on how test scores varied with free and reduced price lunch status, pre-K participation, and pre-K participation interacted with free and reduced price lunch status, as well as published information on the standard deviation of test scores at kindergarten entrance.  To compute percentile gains at kindergarten entrance by group, I assumed that the test score distributions were normal, and test score distributions were calculated with the overall average at kindergarten entrance set at the 50^th percentile. Calculations were done separately for each of the four tests and then averaged. The average effect size of the higher-income group is 34% below that of the lower-income group. However, because the lower-income group tended to be further away from the entrance mean than the higher-income group, the percentile gain differentials are somewhat less.)

The Boston test score gains for pre-K for middle-class sufficient are large enough to easily pass a benefit-cost test. Boston’s pre-K program appears to be relatively expensive, at perhaps $15,000 to $17,500 per student. (Boston’s program is a full-day program, pre-K teachers are paid at the same average salaries as other Boston Public Schools’ teachers, Boston Public School teacher salaries average over $82,000, and Boston’s pre-K classrooms seem to average a class size of 12.3 students.) But the estimated future adult earnings gains based on percentile test score gains at kindergarten entrance are also large. Based on the percentile gains in test scores from Boston pre-K, the ratio of the present value of the future increase in adult earnings, to the cost of the program, are estimated to be $3.22 for children eligible for a subsidized lunch, versus $2.30 for middle-class children.

(Note on calculations: I adjusted estimated earnings effects from Chetty et al., as used in Bartik/Gormley/Adelstein, for the higher Boston vs. Tennessee prices using the price indices in Aten, as well as adjusting to 2012 prices. This resulted in an estimate that each 1 percentile increase in kindergarten test scores will increase the present value of adult earnings by $2,657 in 2012 Boston prices. I multiplied this by the percentile gains computed above to get a total present value of adult earnings gain from pre-K. For these calculations, I assumed the average pre-K cost per student in Boston was $17,387. This is based on adjusting the numbers for pre-K costs for full-day pre-K that pays public school salaries, in the “Meaningful Investments in Pre-K” study by the Institute for Women’s Policy Research, for Boston’s higher teacher salaries, higher prices, and lower class size. Class size estimates are based on the report in Weiland and Yoshikawa that there were 2938 eligible children in 238 classrooms, although this includes both pre-K and kindergarten classrooms.)

These Boston benefit-cost results are similar to the estimates by Bartik/Gormley/Adelstein for Tulsa. The Tulsa results for full-day pre-K estimated a benefit-cost ratio for future earnings benefits relative to pre-K costs of 3.09 for children eligible for a free lunch subsidy, versus 2.82 for children whose family income was too high to quality for a lunch subsidy.  Pre-K is more expensive in Boston than in Tulsa, but the higher Boston earnings mean the earnings benefits are greater as well.

The Boston and Tulsa studies both suggest that pre-K has broad benefits for many income groups. Pre-K provides services in terms of social skills, as well as cognitive skills, that are hard for many families to develop for their children as well on their own.

For both substantive and political reasons, pre-K programs that provide broad access to many groups make sense. Not only is this politically more attractive, but universal access pre-K programs will provide higher overall benefits for the local and national economy. If we want to truly upgrade the overall quality of the local labor force, we need pre-K programs that provide high-quality services to a high proportion of all children.