High School Longitudinal Study of 2009The High School Longitudinal Study of 2009 (HSLS:09) is a nationally representative, longitudinal study of more than 21,000 9th graders in 944 schools who will be followed throughout their secondary and postsecondary years. The study focuses on understanding students' trajectories from the beginning of high school into postsecondary education, the workforce, and beyond. What students decide to pursue when, why, and how are crucial questions for HSLS:09, especially, but not solely, in regards to science, technology, engineering, and math (STEM) courses, majors, and careers.