Assessments were conducted four times each school year, approximately 70–90 days apart. Students completed an online questionnaire, in English or Spanish, in a school computer lab under staff supervision. Assessments were completed in 8–10 minutes, with younger students and first-time participants requiring the most time. Students were able to opt out of participation at any time during the survey, without penalty, by clicking a button. At each student’s first survey, sex, race, ethnicity, and prior lifetime substance use were assessed.
