junior high vs middle school

junior high and middle school both are nouns.

Word	Noun	Adjective	Verb	Adverb
junior high	Yes	No	No	No
middle school	Yes	No	No	No

As nouns, middle school is a hypernym of junior high; that is, middle school is a word with a broader meaning than junior high:

junior high: a secondary school usually including 7th and 8th grades
middle school: a school for students intermediate between elementary school and college; usually grades 9 to 12

Other hypernyms of junior high include Gymnasium, lycee, lyceum, secondary school.

junior high (noun)	middle school (noun)
a secondary school usually including 7th and 8th grades	a school for students intermediate between elementary school and college; usually grades 9 to 12