A systematic random sample selects grade-eligible schools from each participating jurisdiction's stratified frame of public schools. The school sample design uses a selection probability proportional to the estimated grade-specific enrollment of the schools. As a result, large schools are more likely to be selected than small schools.
Each cooperating sampled school administers one or more assessment sessions. The number of sessions administered depends on the school's estimated grade-specific enrollment.
Numerous features highlight the detailed school sample selection process: