A supplemental sample of new public schools reflects additions to the target population that occur after the creation of the sampling frame. New public schools include:
recently opened schools that are not listed on the original sampling frame, and
schools existing on the sampling frame that changed grade spans to include an eligible grade.
Because public schools are organized into districts, and district personnel (not school personnel) will be knowledgeable about the existence of new schools, a sample of school districts is selected in order to compile lists of new schools. A school district level file constructed from the Common Core of Data (CCD) public school file forms the district sampling frame. The CCD public school file, maintained by the National Center for Education Statistics, contains information about elementary and secondary schools in the 50 states, District of Columbia, and outlying areas.
The district sampling frame separates school districts into two groups:
small districts contain at most three schools and no more than one fourth-grade, one eighth-grade, and one twelfth-grade school; and
medium/large districts contain four or more schools, two or more fourth-grade schools, two or more eighth-grade schools, or two or more twelfth-grade schools.
The selection of new schools excludes small school districts. School recruitment during the state assessment identifies any new schools in the small school districts.
The district sampling frame yields a sample of school districts to contact regarding the existence of new schools. The school district sample includes all school districts from those participating jurisdictions that sample all eligible schools. For each of the other participating jurisdictions, the school district sample includes a combination of 10 medium and large school districts.
To create this school district sample for a participating jurisdiction, the medium and large school districts in the jurisdiction are first sorted by student enrollment, from the smallest enrollment to the largest enrollment. The student enrollments of the sorted school districts are summed, starting with the district with the smallest school enrollment. Summing is stopped at the school district that causes the cumulative student enrollment to exceed 20 percent of the jurisdiction's student enrollment. All school districts in the sorted list above (but not including) that school district forms the smaller district sampling group, while all other school districts form the larger district sampling group.
Two school districts are selected from the group of smaller school districts with equal probability. Eight school districts are selected from the group of larger school districts with probability proportional to student enrollment. For jurisdictions with less than eight school districts in its larger district group, all school districts from the larger district group are selected, as well as enough districts from the smaller district group to make a total sample of 10 districts.
Each selected school district receives a list of its public schools that appear on the original school sampling frame. These districts, in return, provide information about either new schools or new grade-eligible schools not included on the lists. These new school data form the sampling frame for the selection of new schools.
From each participating jurisdiction's new school data comes a sample of new schools. The following formula gives the probability of the selection of a school within a jurisdiction:
sampling rate equals the sampling rate used for the particular jurisdiction in the original school selection sample,
measure of size equals a standardized measure of the school's estimated grade enrollment (see Estimated Grade Enrollment and Measure of Size for more information), and
P(district) equals the probability of selection of a school district within the particular jurisdiction.
Newly grade-eligible schools within the new school sample keep the measure of size calculated during the original school sample.
The new school sample includes two additional groups of schools. First, it adds all new and newly grade-eligible schools found during the field period for medium and large school districts in participating jurisdictions that sample all eligible schools. Second, it adds all new and newly grade-eligible schools coming from small school districts that have a school selected in the original sample.