I mentioned this error before, so here’s a grim reminder not to make it. Perry Bible Fellowship is a rather grim comic anyway, even if it is funny to those of us with a grim mind set.
The error is made by both the students and the, um, professor, and the error is promulgated by lots of stuffy English teachers, so it’s fairly common.
That “preposition” at the end of the sentence isn’t a preposition. It’s an adverb! It’s part of a separable verb, of which English has many. (Or I might say, “…which English has many of.”)
Those words, which can also be used as prepositions in other contexts, are perfectly correct at the end of a sentence when they’re part of the verb. It brings to mind the apocryphal Winston Churchill quote, said when someone correct his English, “Impertinence, young man, is something up with which I will not put.”