When you know your teacher has completely given up.

Congratulations, kid. Your determination to write your paper in tiny, illegible handwriting has finally pushed your teacher over the edge from "I can at least take a modicum of pleasure in failing these YOLO-spewing idiots into oblivion" to "Fine, whatever — just let me coast through these last few years until I can pick up my pension." If there's one strategy where American children might have an edge over their well-mannered Asian counterparts, it's annoying their elders into surrender.