Sample and Assignment to Condition

Preschool programs taking part in the evaluation of the curricula included Head Start centers, private child care centers, and public pre-kindergarten programs in urban, rural, and suburban locations. Each research team recruited interested local preschool programs. IES had set a funding priority on grant applications that addressed preschools serving children from low-income families, with the result that 88 percent of the preschools included were either Head Start centers or public pre-kindergarten programs, and half of the children’s primary caregivers had a high school education or less. Programs agreed to the random assignment (by program or classroom) to a treatment curriculum or to local control conditions.

For each evaluated curriculum, table B indicates whether pre-kindergarten programs or classrooms were randomly assigned to treatment or control conditions, the number assigned to each, and the number of treatment and control students included in each evaluation. Three teams (implementing four curricula) randomly assigned pre-kindergarten programs, and the other nine teams randomly assigned classrooms. Three teams compared two curricula against a single set of control classrooms or programs. All but two teams (Purdue University and University of New Hampshire) used block random assignment.

The process of random assignment differed somewhat depending upon the evaluator. The seven research teams working with RTI were responsible for the random assignment at their sites; RTI monitored the process and tracked any changes. These teams had a pilot preschool implementation year starting in the fall of 2002. The randomization conducted in that year carried over, in most cases, to the actual evaluation begun in the 2003-04 school year. The five research teams working with MPR began implementing the curricula in the 2003-04 school year. In conjunction with the research teams, MPR conducted block random assignment for four teams. In addition, Florida State University (FSU) block randomly assigned pre-kindergarten programs to its two curricula and the control group.

The analyses included 2,911 children, 315 preschool classrooms, and 208 preschools. As noted above, the PCER study individually evaluates separate curriculum so no comparisons are made between all those included in the treatment condition and all those who were part of the control condition. Such comparisons are made for each evaluation’s treatment and control groups in chapters 2 to 13.

On average, the students were age 4.6 years at the time of the baseline data collection in the fall of 2003 and age 6.1 years at the time of the kindergarten follow-up in the spring of 2005. Approximately half (51%) of the children were male. One-third were white non-Hispanic, 43 percent were African American, and 16 percent were Hispanic. Less than 7 percent had a disability. On average, the students’ primary caregivers, most often their biological or adoptive mother, were age 32 years at the time of the fall 2003 data collection. Less than half (47%) were married and one-third were never married. Less than half attended or graduated from college (48%), one-third had a high school diploma or GED, and 19 percent did not complete high school. Half were employed full-time, 14 percent part-time, and 34 percent were unemployed.

Almost all the preschool teachers were female (98%) and the majority were White (54%), with one-third African-American. Two-thirds had at least a college degree. On average, they had 12 years of teaching experience and 8 years of experience teaching in pre-kindergarten settings. A majority (87%) of the preschool programs in which they taught were full-day programs. More than half (58%) were public pre-kindergartens, 31 percent were Head Start teachers, and child care teachers made up the remainder (12%). On average, teachers taught 15 students, with a child-staff ratio averaging 7.5 children per teacher.

The kindergarten teachers were also mostly female (98%) and White (74%), with 17 percent African-American. Almost all had at least a BA (97%) with 39 percent having a graduate degree. They averaged 15 years of teaching experience, with an average of 9 years teaching kindergarten. Ninety-three percent of the kindergarten classrooms were full-day and 92 percent of the students were enrolled in public schools. The average number of students per classroom was 20 children. Thirty-nine percent were enrolled in schools where more than 75 percent of the students were eligible for free or reduced-price lunch.

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