No it isn't. Latin-based grammars trumpeted this "rule" for many years[1], but those days and that theory of English grammar are long gone. In Churchill's words: "This is the sort of English up with which I will not put."

Edit: I don't disagree with the gist of your advice, of course. This is just a bizarre illustration of "know your audience," and would be even if the grammatical rule you chose were correct. "Know your audience" is about much more than grammar.

1. The reasoning being that in Latin it's impossible to end a sentence with a preposition, and thus, obviously, to do so in English is simply badwrong.