"The teacher left the class before I came in."
Translation:Учитель вышел из класса до того, как я вошла.
«Учитель покинул класс» is technically possibe, but sounds very unnatural IMHO. «Покинул» sound way too poetic for such a trivial matter as leaving the class.
I'm a native of Russian too, and I would consider «Учитель покинул класс» to be an error of style. However, this judgement is based mostly on my intuition as a native speaker, and I don't have references to back it up; I believe you don't either (?), so arguing on this seems pointless.
The problem is not in the verb "покинул", but in the fact that the phrase is not conversational. One would rather say just "Учитель вышел" without an object. If you need to specify the object it most likely means that you're writing this sentence (for example in police report). In that case word "покинул" fits perfectly fine.
In English infinitive can be used as an object: before I came in. In Russian you can't say so, it'll be a mistake.
The most similar construction that I can come up with would be: before my coming in = до моего вхождения, but even though this phrase is gramatically correct in Russian it sounds scientific if not vulgar.
Instead one would rather use the following structure in Russian: before the moment, when I came in = до того [момента], как я вошёл.
It's just the way we speak.
It's necessary if followed by the object. You'd have to omit it if the phrase would be composed like this:
- Я вошла, но учитель вышел из класса раньше - completely analogous to English as I see it: "I came in but the teacher left the class earlier"
- Учитель вышел из класса раньше меня - in this case the meaning of the sentence is different: I also exit the room like the teacher does
If you ask specifically about the "чем" word, not another. Yes, you can replace it with a more old-fashioned "нежели"
He could leave the class не выходя (using/stamping feet). He could: fly out the window, fall through the floor, just mystically disappear, crawl out, run out, jump out, fall out... etc. All of these moving methods may well be “left,” but not one of them is “вышел”. That is why my option "Учитель покинул класс" sounds not only better, but even more correctly And more than suitable here, I suppose. Reported.