This is the first study to use longitudinal, nationally-representative U.S. data to examine the relationship between early elementary school ADHD diagnosis and adolescent academic achievement. Although results are consistent with prior work that claims children with more severe behaviors fare worse academically than those children with relatively less severe ADHD behaviors, this study shifts the focus to an often neglected group: children who are diagnosed with ADHD but who have relatively minor ADHD-related behavior problems.