Behavioral Health Coordination and Communication Act of 2021 This bill establishes, within the Executive Office of the President, the position of Interagency Coordinator for Behavioral Health to coordinate federal programs and activities concerning mental health and substance use disorders. Federal departments and agencies must notify the coordinator when developing or implementing policies related to behavioral health. The Government Accountability Office must report on the impact of the coordinator on relevant programs and must study issues related to behavioral health services in school settings and in the juvenile justice system.