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The Results of the Preschool Experiment

The Perry Preschool was started by David Weikart when he was director of special services for the public schools in Ypsilanti, Michigan. There was no such thing as preschool at this time, and experts and school officials were initially skeptical of his idea. They thought 3- and 4-year-olds were too young learn. Weikart convinced them to let him try the idea if he set it up as an experiment to answer this question: does preschool work?

The preschool was funded with special education money from the State of Michigan. It was set up in the gym of what was then the district's all African-American elementary school, the Perry School.

Weikart and his research staff identified 123 African-American children from low-income homes who were considered at risk of school failure because of low scores on intelligence tests. Then they flipped a coin to determine who would be in the preschool.

A total of 58 children went to the preschool over the course of five years; they are called the "preschool" group. Sixty-five children were assigned to a control group that received no preschool; they are called the "no-preschool" group.

The children were randomly assigned so that the only statistically significant difference between the two groups would be the experience of going to preschool; in other words, the best explanation for any group differences in subsequent performance is preschool.

A randomized trial like this, with a study group and a control group, is the most rigorous research method for measuring the effectiveness of an intervention. This is the type of study the FDA requires for new drugs.

The Preschool

The Perry Preschool was a half-day program for 3- and 4-year-old children. Students and their mothers also received home visits with a teacher once a week for 90 minutes. The preschool operated for eight months of the year, from 1962 until 1967. Most children attended the preschool for two years.

There were roughly 25 students in each preschool class, with four teachers. All of the teachers were certified in elementary and special education and had training in early childhood development.

Study Results

Researchers collected data on both the "preschool" and "no-preschool" groups every year from ages 3 through 11, and again at ages 14, 15, 19 and 27. The most recent data was collected when the study participants were 40 years old. The researchers are hoping to collect more data about participants in their 50s; the researchers are specifically interested in the possible health benefits of going to preschool.

At the age of 40, 112 of the study participants were tracked down and interviewed; two participants refused to be interviewed; two could not be found; and seven had died.

Over the course of their lifetimes, members of the preschool group did better than the no-preschool group in many ways. Below is a summary of the study's most significant findings.

Intellectual Performance

Researchers used the Stanford-Binet Intelligence Test to assess children's intellectual abilities (their IQ). To be eligible for the study children had to have IQ scores that qualified them as "borderline educable mentally impaired," as defined at the time by the American Association on Mental Deficiency (now known as the American Association on Intellectual and Developmental Disabilities). Most of the children in the study had initial IQs between 70 and 85.

  • By the end of their second year of preschool, the preschool group significantly outscored the no-preschool group on the Stanford-Binet IQ test. The adjusted mean score for the preschool group was 94.8. For the no-preschool group, it was 83.6.
  • The preschool group continued to outscore the no-preschool group on IQ tests until age 8. Then their Stanford-Binet IQ scores started to go down and there were no significant differences in scores between the two groups. Other tests of intellectual and language ability showed initial gains among the preschool children, but most of these differences also "faded out" after a few years.

Education

The preschool group did better in school in a number of ways. They performed higher on achievement tests, they got better grades, they spent more time on their homework. The evidence suggests they liked school more - they were more committed to school - than their peers who did not go to preschool. The preschool group was also less likely to end up in special education classes for what was called "mental impairment." The preschool program had more effects on girls in school than on boys; girls were less likely to repeat a grade, less likely to drop out, and more likely to graduate from high school. The preschool program did not have effects on boys in these areas.

  • Educational Attainment:
    • Children in the preschool group were much more likely than those in the no-preschool group to graduate from high school. By age 40, 77 percent of the preschool group but only 60 percent of the no-preschool group had graduated from high school in some way (some of them dropped out but eventually earned GEDs).
    • All of the difference in high school graduation rates was because of girls. By age 40, 88 percent of the preschool group females had graduated from high school in some way, but only 46 percent of the no-preschool group females had high school degrees. For males, there was no difference in high school graduation rates. By age 40, 68 percent of the preschool group males had high school degrees, compared to 69 percent of no-preschool group males. Another way to say it: Going to preschool nearly doubled a girl's chances of getting a high school degree, but had no effect on boys.
    • The vast majority of study participants did not go to college. By age 40, 9 percent of the preschool group had an associate's degree or higher; 5 percent of the no-preschool group had some sort of college degree.

  • Special Education:
    • The children who went to preschool were significantly less likely to be placed in special education classes for mental impairment (based partly on low IQ scores). More than one-third of the children who did not go to preschool were placed in special education for mental impairment, while only 15 percent of the preschool children were placed in those classes.
    • The preschool had a much bigger impact on the girls' chances of being placed in special education for mental impairment. Only 8 percent of the girls who went to preschool were assigned to special education for mental impairment, while 36 percent of the girls who did not go to preschool were put in those classes. The difference for boys was smaller; 20 percent of the boys who went to preschool were assigned to special education for mental impairment, while 33 percent of the no-preschool boys were.
    • The preschool had a big effect on whether girls repeated grades or dropped out of school, but it had almost no effect on boys in these areas.
  • Achievement Tests and School Performance:
    • The preschool group outperformed the no-preschool group on various achievement tests and measures of adult literacy. Differences in achievement were small when the children were in elementary and middle school, but then big differences showed up at age 14, as the study participants entered high school.
    • At age 14, the no-preschool group scored at the 6th percentile on achievement tests while the preschool group scored at the 13th percentile. This is a significant difference between groups, even though both scored low. "The reader should keep in mind that both groups were at risk of school failure," write the researchers in their report. "The proper comparison is between groups rather than with the overall population, which is what percentiles do."
    • There were significant differences in high school grade point average (GPA) between the two groups. As with achievement test scores, the study participants had fairly low GPAs, but the preschool group did better than the no-preschool group. The preschool group had an average GPA of 2.03 while the no-preschool group average was 1.73 (A=4 and F=0). As with high school graduation, most but not all of the difference between groups was because of girls. Boys who went to preschool had slightly higher GPAs (1.82 vs. 1.72); girls who went to preschool had significantly higher GPAs (2.35 vs. 1.71).
    • On adult tests of skills and literacy, the preschool group scored higher than the no-preschool group too. The differences were small in most areas except occupational knowledge and awareness of health information. In these two areas, the preschool group scored significantly higher than the no-preschool group.

  • Behavior and Attitudes toward Education:
    • On a variety of measures, people who went to preschool and their parents had significantly more positive attitudes toward education. Children who went to preschool also had fewer behavior problems in elementary school.
    • According to the ratings of teachers in kindergarten through third grade, the preschool group engaged in personal and school misconduct significantly less frequently than the no-preschool group.
    • At age 15, the preschool group placed significantly greater importance on high school than the no-preschool group. They spent more time on their homework and they were more likely to say they thought about going to college. Looking back on their high school experience at age 19, the preschool group expressed significantly better attitudes about high school than the no-preschool group.
    • The parents of the preschool participants had more positive attitudes toward their children's education. Significantly more of them said their teenage children enjoyed talking about what they were doing in school. The preschool parents were also more likely to say their children had done as well in school as they would have liked, and that they hoped their children would get college degrees.

Economic Performance:

The people who went to preschool were more likely to be employed and they earned significantly higher incomes than the people who did not go to preschool. Members of the preschool group were also more likely to own homes and cars, and to have savings accounts. And they were less likely to receive social services.

  • At age 40, 76 percent of the preschool group was employed compared to 62 percent of the no-preschool group. Interestingly, this overall difference in employment rate at age 40 was due to the fact that 70 percent of the preschool males were employed compared to only 50 percent of the no-preschool males. It was the reverse at age 27. At that time there was no significant difference in employment for preschool vs. no-preschool males (both about 60 percent). But females who had gone to preschool were much more likely to be employed at age 27 than females who had not gone to preschool (80 percent vs. 55 percent).
  • At age 40, medial annual earnings for people who had gone to preschool were about $21,000. Earnings for people who had not gone to preschool were about $15,000.
  • At age 40, 37 percent of the preschool group owned homes versus 28 percent of the no-preschool group. And 82 percent of the preschool group owned a car, while 60 percent of the no-preschool group did.
  • More of the group who went to preschool had a savings account at age 40 (76 percent vs. 50 percent).
  • By age 40, 86 percent of the no-preschool group had received social services in their adult lives, while 71 percent of the preschool group had received services. For family counseling in particular, significantly fewer of the preschool group had received services (13 percent vs. 24 percent for the no-preschool group).

Crime

Probably the most significant finding of the Perry Preschool Study is the effect it had on crime. The odds of being arrested by age 40 were half as great for the people who went to preschool. In other words, it appears going to preschool cut a person's chances of being arrested in half. The biggest effect was on men, who tend to commit more crimes than women.

  • More than half of the people who did not go to preschool had been arrested by age 19.
  • By the age of 40, the no-preschool group had significantly more lifetime arrests than the preschool group. More than half of the people who had not gone to preschool had been arrested five or more times. Arrest rates were also high among the preschool group, but not as high; 36 percent of the people who did go to preschool were arrested five or more times by age 40.
  • By the age of 40, 21 percent of the people of the no-preschool group had spent time in prison compared to only 9 percent of the preschool group.
  • In terms of violent crimes, the preschool group had fewer arrests by age 40 (32 percent vs. 48 percent ever arrested for violent crimes). The preschool group was also less likely to be arrested for property crimes (36 percent vs. 58 percent ever arrested), and for drug crimes (14 percent vs. 34 percent ever arrested).
  • Going to preschool appears to have had a particularly significant effect on crimes people committed during their adult years from age 28 to 40. In this period of life, the odds of a person from the preschool group committing a violent crime was 83 percent lower than someone in the no-preschool group; the odds of a person from the preschool group committing a property crime was 61 percent lower than someone in the no-preschool group.

Relationships and Drug Use

Going to preschool had positive effects on people's relationships. The people who went to preschool were also slightly less likely to use drugs.

  • Men who went to preschool were more likely to be involved in raising their children than men who did not go to preschool (57 percent vs. 30 percent). And at age 40, men who went to preschool were more likely to be married (43 percent vs. 25 percent).
  • At age 40, people who went to preschool were more likely than the no-preschool group to say they were getting along very well with their families (75 percent vs. 64 percent) and when asked how their family members thought they were doing in life, the preschool group was twice as likely to say their families thought they were doing great.
  • Illegal drug use was a significant problem in the 1970s and 80s, especially in the neighborhoods where many of the study participants lived. The interviews conducted at age 40 included several questions about drug and alcohol use. Overall, the findings show much higher rates of use by people in both the preschool and no-preschool groups compared to the general population. However, it appears that going to preschool had some effect on drug use, especially among males. Men who did not go to preschool were more than twice as likely to report using sedatives, sleeping pills, or tranquilizers. They were also more likely to report using marijuana and heroin.


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