Agreement!

Here's another good one:

I spent most of my career in a college-prep school in Georgia in which the headmaster was, unfortunately, an insufferable little poseur. One of his "accomplishments" was to get a wealthy redneck from Florida to endow a library (which, incidentally, the redneck never paid for because he got upset when his daughter didn't get into University of Georgia). Anyway, the headmaster, ever the visionary, had these words inscribed over the entrance way:

"In this library lies the wisdom of the past and the hope of the future."

Well, it should be "lie," not "lies." Get it? And he taught AP English !