middle school vs Gymnasium

middle school and Gymnasium both are nouns.

Word	Noun	Adjective	Verb	Adverb
middle school	Yes	No	No	No
Gymnasium	Yes	No	No	No

As nouns, middle school and Gymnasium are synonyms defined as:

middle school and Gymnasium: a school for students intermediate between elementary school and college; usually grades 9 to 12

Other synonyms of middle school include lycee, lyceum, secondary school.

middle school (noun)	Gymnasium (noun)
a school for students intermediate between elementary school and college; usually grades 9 to 12	a school for students intermediate between elementary school and college; usually grades 9 to 12