From Longman Dictionary of Contemporary Englishschoolmarmschool‧marm /ˈskuːlmɑːm $ -mɑːrm/ noun [countable] OLD-FASHIONEDa woman who is considered to be old-fashioned, strict, and easily shocked
Examples from the Corpus
schoolmarm• It seems the schoolmarm entered some confusion into their heads.Origin schoolmarm (1800-1900) school + marm ((19-21 centuries)) (from ma'am) 