classroom vs home room

classroom and home room both are nouns.

Word	Noun	Adjective	Verb	Adverb
classroom	Yes	No	No	No
home room	Yes	No	No	No

As nouns, home room is a hyponym of classroom; that is, home room is a word with a more specific, narrower meaning than classroom:

classroom: a room in a school where lessons take place
home room: a classroom in which all students in a particular grade (or in a division of a grade) meet at certain times under the supervision of a teacher who takes attendance and does other administrative business

Other hyponyms of classroom include homeroom, lecture room, study hall.

classroom (noun)	home room (noun)
a room in a school where lessons take place	a classroom in which all students in a particular grade (or in a division of a grade) meet at certain times under the supervision of a teacher who takes attendance and does other administrative business