This study compared the high school academic experience of adolescents with and without childhood ADHD using data from the Pittsburgh ADHD Longitudinal Study (PALS). Participants were 326 males with childhood ADHD and 213 demographically similar males without ADHD who were recruited at the start of the follow-up study. Data were collected yearly from parents, teachers and schools. The current study used assessment points at which the participants were currently in or had recently completed grades 9, 10, 11, and 12. Results indicated that adolescents with ADHD experienced significant academic impairment in high school relative to comparison adolescents, including lower overall and main academic subject grade point averages (GPA), lower levels of class placement (e.g. remedial vs. honors), and higher rates of course failure. In addition, teacher reports indicated that adolescents with ADHD completed and turned in a significantly lower percentage of assignments and were significantly less likely to be working up to their potential. Adolescents with ADHD were also significantly more likely to be absent or tardy during the academic year, and they were over eight times more likely than adolescents without ADHD to drop out of high school. These findings demonstrate that children with ADHD continue to experience severe academic impairment into high school.