There is nothing in the DSM criteria that speaks to the childs intelligence. What defines ADHD is symptoms and intelligence is never mentioned. In fact many people with ADHD are very intelligent. You need to find a good doctor that specializes in ADHD and have your child evaluated. Then walk into a meeting with a diagnosis from a doctor. If they ignore that – then the fun can begin. Check out this link. https://www.helpguide.org/articles/add-adhd/diagnosing-attention-deficit-disorder-adhd.htm#children