Geraldine Grundy has been depicted as a Math teacher, English teacher, History teacher, and Drama teacher at Riverdale High School. Her last name is a pun on the theatrical character "Mrs. Grundy" introduced in "Speed the Plough" (1798) by Thomas Morton (1764-1838). Mrs. Grundy in the play was the personification of the tyranny of conventional propriety. By the 19th century the term "Mrs. Grundy" had become synonymous to the term "prude". Miss Grundy was thus introduced as prudish old spinster, keeping a watchful eye on her students.
Since her introduction in the 1940s, Grundy has been developed to a more likeable figure. She deeply cares for her various students and pushes them to develop their skills through her lessons. She also convinces various students to use their personal skills in ways that benefit both themselves and the school community. The students tend to grumble at the efforts demanded of them but seem to genuinely respect and even like Grundy, the teacher trying to make the difference at their lives. She has proven herself to be a particularly insightful person, often seeing through schemes that fool the other teachers and even fool Mr. Weatherbee; she usually manages to get the upper hand even with characters as wily as Jughead and Veronica, something no other teacher accomplishes.
Grundy grew up on a farm in a rural small town before her family moved to Riverdale; as a teenager at Riverdale High, she was part of a romantic triangle involving Weatherbee's twin brother Tony and Hermione, the woman who grew up to become Veronica Lodge's mother. She served in the Military, as a WAC, and actually outranks Mr Weatherbee. She has an unusually strong bond with Jughead Jones and is the only teacher he truly respects (though he grumbles about her all the same) and the only teacher to successfully push him to live up to his potential (sometimes).
In Life with Archie #6, Ms Grundy died of cancer.