High school or senior high school is the education students receive in the final stage of secondary education in the United States. In the United States, this lasts from approximately 13/14, 14/15, or 15/16 to 17/18 years old in most cases. Most comparable to secondary schools, high schools generally deliver phase three of the ISCED model of education. High schools have subject-based classes. The name high school is applied in other countries, but no universal generalization can be made as to the age range, financial status, or ability level of the pupils accepted. In North America, most high schools include grades nine through twelve. Students attend them following graduation from middle school (or alternatively from a junior high school). From Wikipedia
