This study uses high school transcript data from the National Assessment of Educational Progress (NAEP) High School Transcript Study (HSTS) to determine the validity of student-reported high school courses on the NAEP twelfth-grade student questionnaire. Given that the HSTS is not administered as part of every NAEP twelfth-grade assessment, self-reported course data are often used to better understand NAEP assessment findings; therefore, it is important to determine the validity of these data. Using multiple administrations of HSTS, this study investigates whether student course reporting has changed over time. The report also examines how self-reported courses may affect the reporting of outcome measures, such as the relationship between course-taking and achievement as reported on NAEP.