prep vs school assignment

prep and school assignment both are nouns.

Word	Noun	Adjective	Verb	Adverb
prep	Yes	No	No	No
school assignment	Yes	No	No	No

As nouns, school assignment is a hypernym of prep; that is, school assignment is a word with a broader meaning than prep:

prep: preparatory school work done outside school (especially at home)
school assignment: work, such as schoolwork or piecework, that is done at home

Other hypernyms of prep include homework, schoolwork.

prep (noun)	school assignment (noun)
preparatory school work done outside school (especially at home)	work, such as schoolwork or piecework, that is done at home