I'm teaching classes of 35+ at a time, and some (not a tiny fraction, either) of my students can't even read English. When new students first come in, before they've gotten used to me, it's not uncommon for me to say, "How are you?" and get a, "네?" in response.
I push them as hard as I can to speak in English, even if it's only one word, but if I didn't allow them to help each other out during classes by allowing them to ask each other how to say different words in English, roughly 3/4 of most classes would end up just sitting there until I could help them all individually. For me, it's a good enough day when they are all trying. And by helping each other out, they're forced to recall all kinds of things and they end up reviewing and learning a lot just by working together.
In some situations, I don't think it's the most productive course of action. To me, it's more important for them to eventually be able to answer me in the target language than it is for them to sit there not speaking Korean and still have no clue what's going on by the end of the class period.
That having been said, I see no need for translation from the teacher. Our classes should be taught in English, even if the students sometimes struggle. It's the only time my kids really have the motivation to try to understand something in spoken English, so it's important.