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. These grades are respectively called Freshman, Sophomore, Junior and Senior. Most comparable to secondary schools, high schools generally deliver phase three of the ISCED model of education. High schools have subject-based classes.