From Longman Dictionary of Contemporary Englishupper classˌupper ˈclass ●○○ noun [singular] (also upper classes [plural]) SSCLASS IN SOCIETYthe group of people who belong to the highest social class —upper-class adjective upper-class familiesGRAMMAR: Singular or plural verb?• The upper class is usually followed by a singular verb: The upper class doesn’t want the system to change.• In British English, you can also use a plural verb: The upper class don’t want the system to change.
Examples from the Corpus
upper class• Constraints on upper class power Scott clearly attributes considerable power to the upper classes in modern Britain. 