State of Our Schools: Pre-K studies

Many studies have examined the impact of high-quality pre-K on the youngest learners. Here are some of the more famous:

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PRE-K Studies:
The Abecedarian Project
Four cohorts of individuals, born into low-income families between 1972 and 1977, were randomly assigned as infants to either the early educational intervention group or a control group. Their progress was observed over time by researchers from the University of North Carolina with follow-up studies at ages 12, 15 and 21.
It found that children who participated had higher cognitive test scores from the toddler years to age 21. They also had higher academic achievement in reading and math from the primary grades through young adulthood.
Participants also completed more years of education and were more likely to attend a four-year college. They were older, on average, when their first child was born. 
Abbott Preschool Program
The New Jersey Supreme Court in Abbott v. Burke mandated the state establish high-quality preschool education in the 31 highest poverty school districts in the state, beginning in the 1999-2000 school year. This was achieved through a mix of private and public programs.
A study by The National Institute for Early Education Research at Rutgers University found that ruling has led to dramatic improvements in both the quality of pre-K classrooms and the performance of children.
NIEER found those who attended the program made strong gains in language, literacy and math at kindergarten entry and that those gains held for students in fourth- and fifth-grades. 
For students who were in the pre-K program for two years, the effects were large enough to close about half of the achievement gap between low-income children and their more advantaged peers. NIEER also estimated that Abbott pre-K reduced grade repetition from 19 percent to 12 percent and special education from 17 percent to 12 percent, through fifth grade.
High/Scope Perry Preschool Study
The study examined the lives of 123 Ypsilanti, Michigan, children born in poverty and at high risk of failing in school. Between 1962 and 1967, at ages 3 and 4, the subjects were randomly divided into a group that received a high-quality preschool program and a comparison group that received no program.
Those who attended the High/Scope Perry preschool had significantly improved IQ scores during and for the first year after their attendance, but those scores soon faded. As the study continued to track participants through age 40, however, longer-term benefits emerged. Those who attended the high-quality pre-K had better school achievement, higher high school graduation rates, higher adult earnings and lower crime rates than peers who did not. They were more likely to own their homes and to be employed and less likely to be arrested, to use drugs or to depend on social services.
Head Start Impact Study
Head Start began in 1965 under President Johnson’s “War on Poverty” as a way to boost school readiness of low-income children. It provides preschool educational services to 3- and 4-year-old children, as well as medical, dental, mental health and nutrition services, and it helps parents to foster their children’s development. When Congress reauthorized the program in 1998, it called for the Department of Health and Human Services to conduct a national study to determine the program’s impact.
That study analyzed 4,667 newly entering 3- and 4-year olds at 383 centers in 23 states. They were randomly assigned to a group that attended Head Start and a control group that was not given access to Head Start but could enroll in other early childhood programs.
An updated report in October 2012 looked at those students through the completion of third grade. It found improved cognitive, social-emotional, health and parenting practice outcomes for Head Start students while they were in preschool. However, almost all of those positive results disappeared by the time the children completed third grade.
The study does not compare pre-K attendance to non attendance, however, as 60 percent of children in the non-Head Start control group still enrolled in some early education program, including about 15 percent who still found their way into Head Start programs. Instead, the study looks at the specific impact of Head Start attendance at age 3 and at age 4.
The Chicago Longitudinal Study
The long-term study has tracked more than 1,400 children born in 1980 into low-income, minority families in Chicago. It compares 957 of those children who received high-quality preschool and early intervention services through third-grade from the Child-Parent Center Education Program to 529 children of similar socioeconomic status who did not.
Researchers from the University of Minnesota found the Child-Parent Center program had a strong positive impact well into adulthood. The most recent report was released in 2011 and tracked those individuals at age 28. It found those who participated in the pre-K program had higher levels of educational attainment, socioeconomic status and job skills and lower rates of substance abuse, felony arrest and incarceration. The greatest impact was observed on males and on children of high school dropouts.