art student vs pupil

art student and pupil both are nouns.

Word	Noun	Adjective	Verb	Adverb
art student	Yes	No	No	No
pupil	Yes	No	No	No

As nouns, pupil is a hypernym of art student; that is, pupil is a word with a broader meaning than art student:

Other hypernyms of art student include educatee, student.

art student (noun)	pupil (noun)
someone studying to be an artist	the contractile aperture in the center of the iris of the eye; resembles a large black dot
	a learner who is enrolled in an educational institution
	a young person attending school (up through senior high school)