"Are you children?"
Would this sentence come across the same way in Czech as it does in English? For example, would a professor say this to a group of immature college students because they are being childish? Or does this sentence only work in the sense that one needs to know whether they are actual children or not?
I think this sentence only works in the sense of being a simple sentence in the earliest stages of a language course where fancy real-life sentences can't be made yet.
As it stands, it wouldn't be uttered by anyone except perhaps by an extraterrestrial who has just arrived on the planet Earth, spots a group of half-sized humans, and wonders what they are.