The "Morbidity and Mortality Weekly Report" ("MMWR") series of publications is published by the Center for Surveillance, Epidemiology, and Laboratory Services of the Centers for Disease Control and Prevention (CDC). Articles included in this supplement are: (1) Overview and Methodology of the Adolescent Behaviors and Experiences Survey--United States, January-June 2021; (2) Use of Tobacco Products, Alcohol, and Other Substances among High School Students during the COVID-19 Pandemic--Adolescent Behaviors and Experiences Survey, United States, January-June 2021; (3) Mental Health, Suicidality, and Connectedness among High School Students during the COVID-19 Pandemic--Adolescent Behaviors and Experiences Survey, United States, January-June 2021; (4) Perceived Racism and Demographic, Mental Health, and Behavioral Characteristics among High School Students during the COVID-19 Pandemic--Adolescent Behaviors and Experiences Survey, United States, January-June 2021; and (5) Disruptions to School and Home Life among High School Students during the COVID-19 Pandemic--Adolescent Behaviors and Experiences Survey, United States, January-June 2021.