old school vs social class

old school and social class both are nouns.

Word	Noun	Adjective	Verb	Adverb
old school	Yes	No	No	No
social class	Yes	No	No	No

As nouns, social class is a hypernym of old school; that is, social class is a word with a broader meaning than old school:

old school: a class of people favoring traditional ideas
social class: people having the same social, economic, or educational status

Other hypernyms of old school include class, socio-economic class, stratum.

old school (noun)	social class (noun)
a class of people favoring traditional ideas	people having the same social, economic, or educational status