course vs art class

course and art class both are nouns.

Word	Noun	Adjective	Verb	Adverb
course	Yes	No	Yes	Yes
art class	Yes	No	No	No

As nouns, art class is a hyponym of course; that is, art class is a word with a more specific, narrower meaning than course:

course (noun)	art class (noun)
a mode of action	a class in which you learn to draw or paint
education imparted in a series of lessons or meetings
facility consisting of a circumscribed area of land or water laid out for a sport
(construction) a layer of masonry
part of a meal served at one time
a connected series of events or actions or developments
a body of students who are taught together
general line of orientation
a line or route along which something travels or moves

course (adverb)	art class (adverb)
as might be expected