A small-town country boy gets a scholarship to Harvard.
During his first week on campus, when he’s still learning to get around the place, he’s trying to find the library to meet up with a study group.
While wandering around, he sees an older, distinguished-looking man walking by.
Figuring that the man is a professor, or otherwise associated with the school, he decides to ask him for directions.
“Excuse me,” he asks, “do you know where the library is at?”
The man stops, looks at him, and sniffs, “Son, at Harvard we do not end a sentence with a preposition”.
“OK. Do you know where the library is at, a**hole?”