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Frequently Asked Questions

Sample Selection

How many children per school did ECLS-K sample?

On average, 23 kindergartners were sampled from each ECLS-K school. In some small schools and early childhood programs offering kindergarten programs, the number sampled was smaller. In some of these smaller schools, the entire population of kindergarten children was selected to participate in the ECLS-K. The average number of children per school decreases with each round of data collection as many children changed schools. For example, approximately one-quarter of children changed schools between kindergarten and first grade, and half of the children had changed schools at least once between kindergarten and third grade.

Did you sample whole classrooms?

No, children in each ECLS-K school were randomly sampled from a list of all kindergartners attending that school. During the design phase of the study, a number of different sample designs were considered and evaluated. The option of sampling entire classrooms was given strong consideration. In the end, this option was not adopted primarily because of the burden such a design would place on the teachers participating in the study and the loss of efficiency associated with an additional level of clustering.

Did the ECLS-K sample include children who were retained in kindergarten? Did it follow children if they were retained in later grades?

Yes, the ECLS-K sample included children who were repeating kindergarten. The base-year sample was composed of children who were kindergartners in the fall of 1998. Approximately 5 percent of these children were in their second year of kindergarten at that time. In addition, about 5 percent of the children who were first-time kindergartners in the fall of 1998 repeated kindergarten during the second year of the study (school year 1999-2000), when the majority of the sample was in first grade.

The ECLS-K did follow children who were retained in later grades. For instance, in the spring of 2002, when most children (89 percent) were in third grade, about 10 percent were in second grade and around 1 percent were in other grades (e.g., first or fourth grade). In the eighth-grade round of data collection (spring 2007), about 87 percent of the ECLS-K cohort was in eighth grade and about 13 percent was in a lower grade. Less than half a percent of the cohort was in a grade higher than eighth.

Were children with disabilities sampled for the ECLS-K?

Yes, children with disabilities were included in the sample for the ECLS-K, though disability status was not used as a sampling characteristic at the time of sampling (i.e., children with disabilities were not sampled at different rates than were children without disabilities). Many of the children in the sample were identified as needing and began receiving special education services over the life of the study. Thus, the sample of children receiving special education services increased in size between kindergarten and eighth grade.

How did the ECLS-K identify children with disabilities?

All children with disabilities who meet federal eligibility requirements are expected to participate in special education programs or receive special education services through the school. During data collection, ECLS-K project staff asked schools whether the sampled children had an Individualized Education Plan (IEP), an Individualized Family Service Plan (IFSP), or a 504 plan on file with the school district. Once children were identified as receiving special educational assistance due to a disability, field supervisors identified what accommodations, if any, needed to be made in order to administer the direct child assessment battery to them appropriately. The special education teachers of children with an IEP, IFSP, or 504 plan were asked to complete questionnaires about their background and the services provided to the children and their families. Additionally, parents were asked a series of questions about children’s health and disabilities in the parent interview.