upper-lower-class vs low-class

upper-lower-class and low-class both are adjectives.

Word	Noun	Adjective	Verb	Adverb
upper-lower-class	No	Yes	No	No
low-class	No	Yes	No	No

upper-lower-class (adjective)	low-class (adjective)
occupying the upper part of the lower class	occupying the lowest socioeconomic position in a society