Megan McArdle is raising concerns about President Obama‘s proposal for high-quality, universal preschool, arguing that successful programs with proven long-term benefits are also highly expensive and labor-intensive.  And it’s true that two of the most carefully studied and clearly effective preschool initiatives—the Perry Preschool program in Michigan and the Abecedarian program in North Carolina—were indeed costly and reliant on relatively large numbers of well-trained teachers.

But there’s another important longitudinal study that followed students who participated in a larger-scale pre-K program than the relatively small-bore, high-cost Michigan and North Carolina experiments. It, too, yielded concrete benefits far beyond the original investment and, along with studies showing powerful shorter-term impacts from more recently created universal programs, strongly suggest that well-designed preschool programs can be implemented successfully on a large scale. The Chicago Longitudinal Study collected data through age 26 on a cohort of over 1,400 students  who participated in the Child-Parent Centers preschool program for low-income families, as well as a control group. Researchers found that the preschool program provided a total return to society of $10.83 for every dollar invested, with the primary benefits arising from increased earnings and tax revenues and averted criminal justice costs.

The program, which was much less expensive and intensive than the Perry/Abecedarian models, included 24 centers located in the poorest neighborhoods in Chicago, each serving 100-150 children aged 3-5 years. Each center was directed by a head teacher and two coordinators, who focused on family support and outreach. The program ran three hours per day, five days a week during the school year, as well as six weeks during the summer. The instructional focus included a structured set of educational activities emphasizing reading and math skills. The child-to-staff ratios were 17 to 2, including a certified teacher and an aide.

It is very rare to find any government program that produces such substantial and carefully documented benefits. Coupled with an abundance of studies demonstrating impressive shorter-term cognitive and behavioral impacts on children in large-scale universal pre-K programs—particularly research on Oklahoma’s initiatives led by William Gormley—the Chicago work reinforces Obama’s case that effective early childhood education can be implemented on a wide scale. Even though the longer-term effects of the more recent initiatives can’t be fully demonstrated because the participants in ongoing studies are still young, the magnitude of the early results is much more positive than it has been for means-tested Head Start and Early Head Start programs.

That raises an important question about President Obama’s initiative: what will become of Head Start and Early Head Start? One of the reasons researchers believe those  more established federal programs have had much less favorable results, both short- and long-term, is that they attempt to provide a broad range of comprehensive services rather than focus their resources more on the classroom instruction emphasized in the successful models. Another disadvantage may be that, because they are means-tested, they lack opportunities for bringing students from all economic backgrounds together in one program. Research by Jeanne L. Reid (who happens to be my wife) has shown that low-income children in socioeconomically diverse pre-K settings demonstrate better outcomes by a variety of measures, with no negative impact on the children from families with higher incomes. Because most federal resources for early childhood flows through Head Start and Early Head Start, it will be interesting to see the extent to which the administration will seek to add funding outside those programs to encourage states to build something new. It is also possible, even likely, that structural reforms to Head Start and Early Head Start will be pursued.

More research on the relative effects of different approaches to pre-K will help to guide policymakers at all levels of government as the trend toward broader and deeper support for early childhood education unfolds. But we already know more than enough to recognize that such efforts should err on the side of ambition rather than caution.