The phrase “high school” should not be capitalized when used in a sentence unless you are referring to a specific high school such as “Langley High School.” You should also capitalize “high school” when used in a headline or title.

Should high school be capitalized?

No, unless the words “secondary school” are part of an official name of a specific school. They would only be capitalized if they were part of a proper noun (a name of a particular person, place, or thing), such as “New York Secondary School,” if there were such a school. Only proper names are capitalized in English.

Is elementary and high school capitalized?

AP Style tip: Capitalize school when part of a proper name: Public School 3, Madison Elementary School, Crocker High School.