Childhood attention-deficit hyperactivity disorder (ADHD) is associated with academic underachievement and school dysfunction. Little is known whether such association varies with the persistence of ADHD symptoms. The authors investigated school functioning among youths with and without persistent ADHD and identified the clinical correlates for school functioning in a large sample of 333 youths with persistent ADHD, 166 with non-persistent ADHD, and 266 without ADHD. The participants and their mothers received structured interviews for diagnosis of ADHD and other psychiatric conditions according to the DSM-IV diagnostic criteria by using the Kiddie epidemiologic version of the Schedule for Affective Disorders and Schizophrenia, and for school functioning by using the Chinese Social Adjustment Inventory for Children and Adolescents. The results showed that both ADHD groups had more impairment in all domains of school functioning than youths without ADHD with a gradient relationship in the order of persistent ADHD, non-persistent ADHD, and non-ADHD. The most consistent correlates for all domains of impaired school functioning were youth- and mother-reported inattention symptoms and increased age. Childhood hyperactivity-impulsivity symptoms also predicted more severe problems in social interactions and school behaviors. Psychiatric comorbid conditions also predicted poorer attitudes toward school works and interactions at school. Our findings indicate that lifetime diagnosis of ADHD, regardless of persistence of ADHD, associate with the impairment of overall school functioning sustaining from childhood into adolescence, and imply that early intervention of childhood inattention may offset school dysfunction at late childhood and adolescence. (Contains 4 tables.)