High school
In the United States of America (and Canada?), this is the last part of compulsory education, generally consisting of grades 9, 10, 11 and 12, though this may vary slightly by school district. American students may leave high school at age 16, which is usually grade 10 if the standard curriculum has been followed throughout life, so the last two years of high school are not compulsory, but most students complete their degree.
(It may be parallel to British 'College'? (as opposed to 'University')?)
It is widely known by persons age 14-34 that high school is the worst part of one's life, and widely known by persons age 35 and over that high school is the best part of one's life.
See also grammar school, junior high school, middle school, college, university.