High school years, generally spanning from ages 14 to 18 years, represent a crucial developmental period in a young person’s life. These years encompass the three phases of adolescence—early (11–14 years), middle (15–17 years), and late adolescence (18–21 years)—each accompanied by a characteristic set of physiologic, cognitive, and psychosocial milestones. This chapter explores the normal growth and development of high school students and provides readers with tools to effectively support adolescents navigate these significant transitions and transformations through their high school journey.