This is PART A of a 3-part, 6-week, double-blind, dose-optimization, parallel-group study in children and adolescents (ages 6-17 years) with ADHD with and without CNVs in specific genes implicated in glutamatergic signaling and neuronal activity. Parts A will include subjects determined to have a specific gene mutation(s) implicated in glutamatergic signaling and neuronal activity.