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SEEP Study Sample
Data were collected from a nationally representative sample of districts and schools in 50 states and the District of Columbia. The study used a stratified random sample of 1,769 schools in 448 school districts and 30 affiliated intermediate education units (IEUs). Twenty state-run special education schools were also randomly selected for participation.

The original sample included about half of the total number so schools, districts, and IEUs ultimately included in the sample. The sampled expanded with the inclusion of additional districts in nine states that contracted with CSEF to conduct individual state SEEP studies. his expanded sample comprises about half of the overall SEEP sample, and the data collected from this supplemental sample are combined with the data collected from the base sample in the SEEP data analyses. All data are appropriately weighted so that samples within the nine states are representative of each of the nine states, and the remaining data are weighted to reflected the population in the remaining 41 states.

State Sample
The state-level data collection included all 50 states and the District of Columbia. Questionnaires were sent o state directors of special education, and completed state-level questionnaires were received from 41 states. The SEEP study team followed up with telephone calls and e-mails until data were collected from all 50 states.

School District Sample
Samples of school districts were selected within each of the states, with a minimum of two districts in each state.(1) Larger numbers of districts were included from larger states. The total sample consisted of 498 regular school districts, IEUs, and state-run special education schools.

The sample included 448 regular school districts and 30 IEUs, selected randomly, with the probability of selection proportional to the number of students enrolled in the district. This sample was selected from a sampling frame of more than 14,000 school districts listed in the Common Core of Data (CCD). Of these 448 districts, 248 districts made up the extended participation sample from the nine contracted states. Districts selected for the national sample were removed from the frame when selecting this extended sample so that they could not be re-selected.

In addition, 20 state-run special education schools were treated as individual school districts, so that fiscal data could be collected using the district-level questionnaires. The 20 state-run special education schools were randomly selected from a frame believed to contain all of the state-operated special education schools in the nation.

School District Central Office Staff Sample
Within each school district, a sample of up to six certified central office staff was selected. Staff were considered to be central office staff if they had offices in the district central office and only worked in schools on an as-needed basis. Examples of such staff include district-level special education administrators, psychologists, social workers, counselors, nurses, and learning consultants. The district director of special education and up to two psychologists were selected to receive this questionnaire for central office staff, along with three other central office staff who were randomly selected using an alphabetized roster. A total of 2,960 central office staff were included in the sample.

School Sample
Samples of elementary, secondary, and special education schools were selected from among the sampled districts and IEUs. Schools from within the total selected sample of 448 districts and 30 IEUs were classified as being either elementary, secondary, or special education schools. A total of 1,769 elementary schools and secondary schools were chosen. This total includes 50 district-run special education schools and one school from each of the 30 IEUs. To represent the nationwide ratio of elementary schools to secondary schools, roughly two thirds of the selected schools were elementary schools. A minimum of two elementary schools, whenever possible, were selected from each district.

Within the regular school districts selected, a sample of 70 schools containing “cluster programs”(2) was assembled. These schools were selected to ensure that sufficient numbers of students with low-incidence, high-cost disabilities who are served in regular schools were included in the sample to generate stable estimates. Cluster program schools that did not serve students with low-incidence disabilities, or had already been selected for the sample, were excluded from the sampling frame. If more than one cluster program school remained in a selected district, one elementary and one secondary school were randomly selected.

Teacher and Aide Samples
Samples of regular education teachers, special education teachers and related service providers, and special education aides were chosen from each selected school. All of the special education teachers and related service providers at each selected school were included in the sample. In addition, six regular education teachers at each selected elementary school and nine regular education teachers at each secondary school were randomly selected using an alphabetized roster and a random number generator. Up to four special education aides were also randomly selected from each elementary school in the sample and up to six special education aides were randomly selected from each secondary school in the sample.

Student Samples
Two types of students were sampled: those who were served within the public schools operated by the sample districts or IEUs, and those who were served outside of their local school district in a non-public school or other public agency. The data for the group of special education students served within the public schools came primarily from questionnaires filled out by special education teachers and related service providers. All special education service providers in the selected schools were asked to fill out questionnaires for two students, and instructions were provided to ensure random sampling. Procedures were also designed to ensure that the service provider most knowledgeable about the student was asked to complete the student questionnaire.

Students with low-incidence disabilities were oversampled (i.e., a higher-than-proportionate number were included) to ensure adequate sample sizes for these less common disability categories. If the class or caseload of a teacher or related service provider included one or two students with low-incidence disabilities, these students were automatically selected for the sample. If there were more than two such students in the class or caseload, two of them were randomly selected using specific procedures provided in the survey materials. If there were no students with low-incidence disabilities, respondents used the procedures to select a random sample of two students with high-incidence disabilities.

Special education students being served outside of their local school district were also included in the sample. District directors of special education randomly selected up to three students placed in nonpublic schools or other public agencies paid for by the school district, selecting from those students with low-incidence disabilities first. The total selected sample of these special education students was 1,520.

To prevent the possibility of a student being selected multiple times, the research team developed sample selection procedures so that students were only selected from the most restrictive placement possible for any given student. The sample selection procedures were designed to ensure that the service provider most knowledgeable about any student was asked to complete the Special Education Student questionnaire about the student.

(1) As Hawaii and the District of Columbia are each considered a single school district, only one school district could be selected from each of these entities.

(2) Within a particular district, special education students with certain low-incidence disabilities are clustered into selected non-special education schools in order to take advantage of economies of scale in meeting their specific needs. For example, if a particular school has a cluster program for visually impaired students, visually impaired students from all over the district would attend that school.

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