The High School Longitudinal Study of 2009 (HSLS:09) is a nationally representative, longitudinal study of over 23,000 9th-graders from 944 public and private schools in 2009. This study follows students throughout their secondary and postsecondary years, examining student trajectories, major/career paths, and STEM interest. The study's Base Year was 2009, the First Follow-up was conducted in 2012, when most of the sample members were 11th-graders, and a brief Update was conducted in 2013, when most sample members would have completed high school.