Skip over navigation

Journal Issue: The Next Generation of Antipoverty Policies Volume 17 Number 2 Fall 2007

Reducing Poverty through Preschool Interventions
Greg J. Duncan Jens Ludwig Katherine A. Magnuson

The Promise of Early Childhood Education

A rigorous body of research demonstrates that very intensive early childhood programs can produce lasting improvements in the life chances of poor children. Recent research also suggests that even less expensive Head Start and pre-K programs may boost early achievement significantly, and in the case of Head Start, improve children’s long-term outcomes as well. By contrast, more typical day care or preschool settings have smaller effects on achievement and behavior. One important lesson is that not all early childhood education programs produce similar effects.

For policy purposes, the goal is not to find the program that produces the biggest benefits but rather to find programs that generate the largest benefits relative to their costs. Programs that generate large benefits but even larger costs are unwise public expenditures. Our proposed program is modeled after early childhood interventions that, according to the best available evidence, appear to generate the largest surplus of benefits relative to costs.

The ability of intensive model programs to improve the life chances of disadvantaged children is illustrated by the well-known Perry Preschool intervention. Perry provided one or two years of part-day educational services and home visits to a sample of lowincome, low-IQ African American children aged three and four in Ypsilanti, Michigan, during the 1960s. Perry Preschool hired highly educated teachers (with at least a B.A.) and was implemented as a randomized experiment. Some mothers and their children were randomly assigned to the Perry program while others were assigned to a control group that did not receive the Perry intervention. The great advantage of randomized assignment is that parents and children in the program of interest can be expected, on average, to be similar at baseline to those randomly assigned to the control group, so differences in outcomes for treatments and controls can be attributed to the effects of the program with a high degree of confidence.

When the children entered school, those who had participated in the Perry program scored higher on IQ tests than those who had not— an impressive nine-tenths of a standard deviation higher.16 These IQ effects, however, disappeared by third grade. Nevertheless, the program produced lasting effects through age forty on employment rates (76 percent compared with 62 percent) and earnings (median annual earnings of $20,800 compared with $15,300 in 2000 dollars) and substantially reduced the chances that participants had ever been arrested (29 percent of the participating children reached age 40 without an arrest as compared with 17 percent of the control group).17

The Abecedarian program, which began in 1972 and served a sample of low-income, mostly African American women from Chapel Hill, North Carolina, was even more intensive than Perry. Mothers and children assigned to the Abecedarian “treatment” received year-round, full-time care for five years, starting with the child’s first year of life. The Abecedarian preschool program included transportation, individualized educational activities that changed as the children aged, and low child-teacher ratios (3:1 for the youngest children and up to 6:1 for older children). Abecedarian teachers followed a curriculum that focused on language development and explained to them the importance of each task as well as how to teach it. High-quality health care, additional social services, and nutritional supplements were also provided to participating families.18 A full-time family nurse practitioner and a parttime pediatrician worked on staff and in the same building as the children. They provided immediate treatment for ear infections, which could have had an effect on the children’s language development.

Abecedarian was a high-cost, high-quality program run by researchers rather than by a government agency. It cost about $18,000 a year for each of a child’s first five years and produced dramatic effects on the future life outcomes of its participants.19 At the start, Abecedarian and control group children had IQ scores that averaged about 1 standard deviation below the mean, as would be expected for children from economically disadvantaged backgrounds. By the time the Abecedarian children reached age five, however, their IQ scores were close to the national average and higher than the scores of children who did not participate. Similarly large effects were observed for achievement on verbal and quantitative tests.20 Nearly fifteen years later, the program’s effect on IQ scores at age twenty-one was smaller than at age five (around 0.38 standard deviation) but still impressive. This problem of partial “fade-out” of the effects of early education, which has been widely documented for a variety of different programs, suggests that sustaining the effects of early interventions on the child’s ability to learn may require highquality follow-up learning environments. We return to this point below.

Although IQ effects faded somewhat over time with Abecedarian, other long-term effects were dramatic and arguably just as important for reducing poverty. For example, children who received the Abecedarian program entered college at 2.5 times the rate of the control group. The Abecedarian intervention also reduced rates of teen parenthood and marijuana use by nearly half. Smoking rates of Abecedarian participants were about 30 percent lower than those of the control group.21 Although employment rates were not statistically different between the Abecedarian and control groups (64 percent compared with 50 percent), children who had participated in the program were about two-thirds more likely to be working in a skilled job (67 percent compared with 41 percent).22 Even with its $18,000 cost and the need to discount benefits accrued in the distant future, the total economic value of Abecedarian’s benefits far exceeded the costs of participating in the program.23

Evidence on the existing publicly funded early education programs, which illustrate what can be achieved for large numbers of children in programs of more variable quality than the one we advocate, is also encouraging. A recent random-assignment experimental evaluation of Head Start found positive short-term effects of program participation on elementary prereading and prewriting for three- and four-year olds equal to about 0.3 and 0.2 of a standard deviation, respectively, but not on advanced skills in these two outcome domains.24 Head Start participation also increased parent-reported literacy skills of children by around 0.45 of a standard deviation. Statistically significant effects on other outcome domains were typically concentrated among three-year-olds, with effect sizes of 0.15 for vocabulary and 0.20 for problem behaviors. Effects on math skills were positive but not statistically significant.25 If one calculates Head Start effects pooling together the three- and four-year-olds in the experiment, however, rather than showing results separately for each age group, the increased statistical power leads to statistically significant program effects on math and almost all of the other main cognitive skill outcomes in the report.26

For policy purposes, the crucial question is whether Head Start effects persist over time; if so, program benefits may be likely to outweigh program costs. Nonexperimental studies of children who participated in Head Start several decades ago suggest lasting effects on school attainment and perhaps criminal activity, although test score effects appear to fade out over time.27 As in the Abecedarian and Perry programs, these effects were large enough that the benefits to society likely outweighed the program costs.

Studies of previous cohorts of children, however, may not provide a good indication of how today’s children will fare. Both centerbased care and early education alternatives to Head Start have proliferated, and many provide enriching environments. In addition, better maternal education and parenting education programs have likely improved the developmental environments of poor children. For this reason we suspect that the benefits of Head Start compared with the most likely alternative for poor children may have declined.

Numerous recent studies have examined the short-term effects of state-initiated pre-K programs on children’s test scores. These studies typically find short-run effects on achievement test scores that are slightly larger than those estimated for Head Start and, importantly, find that participation in the programs improves both language and math skills.28 A study by Steven Barnett, Cynthia Lamy, and Kwanghee Jung of pre-K in five states found effects on receptive vocabulary and math of just over one-quarter of a standard deviation and effects on print awareness of nearly two-thirds of a standard deviation.29 Studies of the Tulsa pre-K program find effects on prereading skills (letterword identification) of around 0.8 of a standard deviation and on early math scores (applied problems) of around 0.38 of a standard deviation.30

How can we explain why the effects estimated for recent state pre-K programs are slightly larger than those for Head Start? One possible explanation is that pre-K programs hire more qualified teachers, pay them more, and offer a more academically oriented curriculum than do Head Start programs. For example, only about one-third of Head Start teachers have completed a bachelor’s degree, whereas all the pre-K programs evaluated by Barnett, Lamy, and Jung had collegeeducated teachers.31 Another explanation is that the Head Start comparison group received more center-based care than did children in the pre-K comparison group.32

A third possible explanation is that the recent Head Start study relies on a rigorous randomized experimental design. Although the recent state pre-K studies are big improvements over past efforts to examine such programs, all are nonetheless derived from a research design that may be susceptible to bias overstating the benefits of pre-K participation.33