Research suggests that mainstream teachers may lack knowledge regarding ADHD and evidenced-based classroom interventions. The purpose of the study was to assess mainstream teachers' knowledge of Attention Deficit Hyperactivity Disorder (ADHD) and support for appropriate classroom interventions to address ADHD concerns within a population of 32 public school teachers from an urban school district in Southern California. Teacher knowledge of ADHD, signs and symptoms, and treatment fell within the mid-ranges of the Knowledge of Attention Deficit Disorders Scale (KADDS) scales. Teachers were mostly supportive of seating children in the front of the classroom, conducting thorough assessments of children's needs and strengths, and using assistive technology in the classroom as classroom interventions to use with children with ADHD. However, were not supportive of the classroom use with many evidence-based interventions designed to help children with ADHD. The majority of teachers wanted more training on ADHD. There were few difference in knowledge based on length of teaching experience, grade level, special education exposure, or ADHD training.