in most school systems in the United States, any three- to six-year secondary school serving students approximately 13 (or 14 or 15) through 18 years of age. Often in four-year schools the different levels are designated, in ascending order, freshman, sophomore, junior, and senior.

The most common form is the comprehensive high school that includes both general academic courses and specialized—commercial, trade, and technical—subjects in its curriculum. There are also many types of specialized schools, agricultural schools, business or commercial schools, trade or vocational schools, and preprofessional schools, such as the High School of Music and Art in New York City and the Bronx High School of Science.

Most American (United States) high schools are public—i.e., tuition-free, supported by state funds. There are, however, a number of private high schools throughout the country, supported generally through a combination of tuition charges and private grants or endowments. Most of these schools offer primarily academic courses to college-oriented students, and many are sectarian. See also secondary education.