This study examines the basic psychometric properties of the Swanson, Kotkin, Agler, M-Flynn, and Pelham Scale (SKAMP), a measure intended to assess functional impairment related to attention deficit hyperactivity disorder, in a sample of 1,205 elementary students. Reliability, factor structure, and convergent, discriminant and predictive validity are evaluated. Results provide support for two separate but related subscales, Attention and Deportment, and provide evidence that the SKAMP predicts school functioning above and beyond symptoms alone. Boys, African American children, and children living in poverty are rated as having higher impairment scores than girls, Caucasian children, and more advantaged peers. Norm-referenced data are provided by gender, race, and parental concern level. This study supports the reliability and validity of the SKAMP in a large, diverse community sample and broadens its clinical utility.