The Big Three

If you ask experts to name the most significant and influential research about preschool, they're likely to name three studies in particular: The Perry Preschool Study, the Carolina Abecedarian Project, and a study of the Chicago Child-Parent Center Program.

These are the "Big Three." But just as the "Big Three" automakers don't rule the car industry anymore, there is lots and lots of research about preschool beyond these three famous studies.

The "Big Three" get the most attention because they are all studies of the long-term impact of early education programs. Perry and Abecedarian stand out in particular because they were set up as randomized controlled trials, a type of scientific experiment most commonly used to test new drugs, but rare in social science and education research.

In both the Perry and Abecedarian studies, researchers designed an early education intervention program and children were randomly assigned to a "treatment" group or a "control" group. The Chicago Child-Parent Center (CPC) study was not conducted this way. It was an analysis of a large public preschool program already in existence, and its size is one of the reasons the study is so significant. The CPC study included more than 1500 children; Perry and Abecedarian included just over 100 children each. All three studies found that preschool has a positive long-term impact on children's lives.

Below are short descriptions of each study, some of the similarities and differences among them, and the results, as well as links to sites where you can read more:

The Perry Preschool Study:

This is the longest-running study of a preschool program. It began in 1962 in Ypsilanti, Michigan. The study involved 123 African American children from poor families. Most children began the program when they were 3 years old and went to preschool for two years. It was a morning program (2.5 hours each weekday) that operated during the school year only (there was no program during the summer months). The ratio of children to teachers was about 6-to-1. Teachers did home visits with families once a week. All teachers had bachelor's degrees and training in special education and early childhood education. The study has so far documented the impact of the program on participants through the age of 40.

Results of the Perry Preschool Program include: higher school achievement; increased high school graduation rate among girls; higher employment rate; higher earnings; and significantly lower crime rate. There were no lasting gains on tests of intellectual performance (IQ tests).

You can read more about the Perry Preschool results here and at

The Carolina Abecedarian Project:

This program began in 1972 in Chapel Hill, North Carolina. It provided early education and health and nutrition services to children beginning when they were about 4 months old until they were 5 years old. The study included 111 children. All were from poor families, and almost all were African American. It was a full-day program that ran for 50 weeks each year. The ratio of students to teachers was 3-to-1 when children were infants and toddlers and 6-to-1 when children were older. When the children entered kindergarten, they were again randomized into a "no further intervention" group and a group that received a "home school resource teacher" who provided additional services. The study participants have been followed through age 21 so far.

Results of the program include: long-term gains on IQ tests (through age 21) and higher school achievement. Program participants were twice as likely to attend a four-year college. They were more likely to have skilled jobs. They were less likely to have their first child before the age of 18. Mothers whose children participated in the program achieved higher educational levels and were more likely to be employed. The study found no difference in crime rates between participants and non-participants. Researchers believe this is partly due to geographical differences: Ypsilanti and Chicago had much higher crime rates than Chapel Hill.

You can read more about the Abecedarian results at, and

The Chicago Child-Parent Center Program (the study of this program is called the Chicago Longitudinal Study):

The Chicago Child-Parent Center (CPC) Program was established in 1967 with funding from Title I of the landmark Elementary and Secondary Education Act of 1965. Some of the centers still operate today.

The CPC program is the second-oldest (after Head Start) federally funded preschool program in the United States. The centers serve families in Chicago's poorest neighborhoods, and require significant parent involvement. Activities for parents include training in child development, parenting skills and nutrition.

The CPC study began in 1986 and is still continuing. It follows 1,539 children. Some of them attended a CPC program; others were part of a comparison group. The comparison group matched the program group closely on a variety of demographic variables including race, poverty and level of parent education. The comparison group children attended other early education programs such as Head Start.

The CPC program begins with preschool for 3- and 4-year-olds and follows up with an enriched curriculum for school-aged children for up to six more years. Teachers in the CPC program have bachelor's degrees and are certified in early childhood education. The ratio of students to teachers is about 9-to-1. There is a parent resource room in each center and a parent resource teacher. The program also includes a school-community representative to conduct home visits and provide referrals for other services such as health and nutrition. The study has documented effects on children through age 15 so far.

Results of the program include: higher levels of school achievement; higher levels of consumer skills; enhanced parent involvement in children's education; lower rates of grade retention, special education and early school dropout; fewer behavior problems in school; and lower juvenile crime rates (adult crime data is still being collected). This study did not measure scores on IQ tests.

You can read more about the Chicago Child-Parent Center Program results at

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