Although attention deficit hyperactivity disorder (ADHD) is among the most heritable psychiatric childhood disorders, social and gene–environment interactions seemingly play an important role in the etiology of ADHD. Consistent with this, this study finds that School‐Wide Positive Behavioral Interventions and Supports (SWPBIS) reduced the likelihood of pharmacotherapeutic treatment for ADHD at age 14–16 by 12%, using population‐wide Norwegian register data and a difference‐in‐difference design (N = 698,364, birth cohorts 1990–2002, 48.7% girls, 5.7% immigrant background). At‐risk students in schools with high fidelity of implementation are driving these intervention effects. Overall, the findings indicate that children with a genetic disposition for ADHD are more likely to avoid medical treatment in an organized and predictable school setting with a focus on positive reinforcement.