I insist: classes for whatever level of English or another language should take place all in English or that other language.
It’s like a game: they may not understand and you’ve got to be understood. How? Speak in another way, give examples, use the whiteboard, make gestures, use words that are cognates with their mother language.
100% or 99% should be in English in my classes. I say 99% because a very few times I might use a word in Spanish, their and my mother language.
So the trend should be all the class in English, even when you are announcing something. The more in English (their target language) the better. Try and use that language in your classes. / Photo from: student in class. www scu edu