The study included a math assessment and survey component in the fall of 9th grade (2009) and again in the spring of most students' 11th grade year (2012). Dropouts were followed with certainty and surveyed again at the same time as the rest of the sample who remained in school.
A brief follow-up data collection occurred in the spring of students' expected graduation year, 2013, to record students' postsecondary options and plans.
A subsequent data collection occurred three years after the expected graduation year (in 2016) to learn about students' postsecondary experiences, and another is tentatively planned to occur in 2025 to learn about participants' choices, decisions, attainment, and experiences in adulthood.
The HSLS population consisted of all ninth-graders across the U.S. enrolled in regular public, Catholic, and other private schools that included 9th and 11th grades.
Students were randomly selected from sampled high schools to participate in HSLS:09. These students' parents and math and science teachers were invited to complete surveys, as were the school administrator and lead school counselor in each selected school.
The base-year study involved a nationally representative sample of 944 high schools, including both public and private schools. An average of 25 ninth-graders per school were selected to participate, which totaled over 24,000 students. From this sample, over 21,000 students responded to the survey.