schoolchild vs pupil

schoolchild and pupil both are nouns.

Word	Noun	Adjective	Verb	Adverb
schoolchild	Yes	No	No	No
pupil	Yes	No	No	No

As nouns, schoolchild and pupil are synonyms defined as:

schoolchild and pupil: a young person attending school (up through senior high school)

Other synonyms of schoolchild include school-age child.

schoolchild (noun)	pupil (noun)
a young person attending school (up through senior high school)	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)