While middle-class children benefit modestly from preschool, youngsters from poor families experience two times the gains in early language and mathematics learning, according to a new study of more than 14,000 kindergartners nationwide.
The report - "The Influence of Preschool Centers on Children's Development Nationwide: How Much Is Too Much?" - also examined whether long hours in preschool centers lead to diminishing returns in children's early development.
Most surprising, according to the researchers based at the University of California, Berkeley, and Stanford University, is that the social skills of white, middle-class children suffer- in terms of cooperation, sharing and engagement in classroom tasks - after attending preschool centers for more than six hours a day, compared to similar children who remain at home with a parent prior to starting school.
Hispanic children with at least basic English proficiency "displayed the strongest cognitive gains after attending preschool with no detrimental effects on their social development," according to Margaret Bridges, a research scientist at UC Berkeley and co-author of the report.
"This may be due to strong socialization practices inside Hispanic homes," Bridges said, "Or, perhaps these families enter quality preschools tightly regulated under growing state and federal initiatives, like Head Start."
"The biggest eye-opener is that the suppression of social and emotional development, stemming from long hours in preschool, is felt most strongly by children from better-off families," said UC Berkeley sociologist and co-author Bruce Fuller.
Cognitive results for African American children are mixed, the researchers said. High attendance rates are associated with gains in language and pre-reading skills, but not with any discernible improvement in knowledge of numbers and math concepts.
The report will be presented Friday, Nov. 4, at a conference of the Association for Policy Analysis and Management in Washington, D.C., and published later this year in the scientific journal Economics of Education Review. It underwent two rounds of academic peer review.
On average, the report finds that the earlier a child enters a preschool center, the slower his or her pace of social development, while cognitive skills in pre-reading and math are stronger when children first enter a preschool program between the ages of two and three.
"Our results for the intensity of attending a center program - measured in hours per week and months per year - are worrisome, while varying across different types of families and children," the report says.
The research team found that more than 1.4 million children, ages three or four, across the nation are enrolled in preschool programs and attend six hours or more daily. About 5.2 million children - including children under age 5 -- attend preschool overall, although Hispanic children are less likely to enter a preschool than white and African-American youngsters. Nearly two-thirds of all four-year-olds nationwide attend a preschool center in the year before starting kindergarten.
A growing list of state governors is making large investments to offer free, publicly-supported preschools for all children, echoing advocates' claims that this will boost the early learning of most children.
"So, the report's a bit sobering for governors and mayors - including those in California, Florida, Georgia, New York, North Carolina and Oklahoma - who are getting behind universal preschool," Fuller said.
Overall, the researchers say it is good news for middle-class parents that their children, on average, benefit cognitively from moderate exposure to preschool centers. Most prior research has focused on preschool's effects on poor children.
But the UC Berkeley-Stanford team says it is bad news that universal access would not likely close early learning gaps. "The magnitude of benefits for poor children is simply insufficient to catch up," the report says. "Instead, extending free preschool to all children - certainly a well-intentioned goal - threatens to simply reinforce disparities in early learning until resources are more carefully targeted on low-income communities."
A report issued last week by the National Institute for Child Health and Human Development (NICHD) found, in its smaller sample of children, that the negative effect of long hours in child care (not limited to preschool) is slowing children's social development well into third grade.
The new UC Berkeley/Stanford report and graphic displays can be found online at: http://pace.berkeley.edu/pace_stanford_berkeley.html.
The study's authors, including Stanford economist Susanna Loeb, UC Santa Barbara economist Russ Rumberger, Stanford doctoral student Daphna Bassok, along with Bridges and Fuller, analyzed data from the Early Childhood Longitudinal Study.
Sponsored by the U.S. Department of Education, the study is tracking children's health, early care and preschool, and elementary school experiences. The main study began in fall 1998, with a sample of about 23,000 kindergartners from about 1,000 kindergarten programs. The youth will be followed through fifth grade.