pupil vs young person

pupil and young person both are nouns.

Word	Noun	Adjective	Verb	Adverb
pupil	Yes	No	No	No
young person	Yes	No	No	No

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

Other hypernyms of pupil include spring chicken, younker, youth.

pupil (noun)	young person (noun)
the contractile aperture in the center of the iris of the eye; resembles a large black dot	a young person (especially a young man or boy)
a learner who is enrolled in an educational institution
a young person attending school (up through senior high school)