The question was asked on social media recently:
When y’all do special person interviews do you let the special person answer in L1?
And like most things in life, the answer is “that depends”.
If the class is beginners, and they just don’t have much language, you don’t really have a problem with this. It’s a non-choice. If you absolutely forbid all use of English, the discussion isn’t likely to go very far. Not only that, but it’s likely that you’ll soon turn a room full of “Target Language is Fun” beginners into a group that dreads language class, since it just means being unable to express anything and feeling inadequate because of it.
Of course, even with beginners, there have to be rules. I strongly recommend some version of my TPRS class rules, or at least something that includes a limitation on English. A limitation, not a ban. A rule limiting the use of English to two words in cases where the person (I can’t guarantee that I’ll know all the words either!) doesn’t know the word in the target language does quite nicely. It controls side conversations (unless they’re having them in the target language, which is a good problem to have) while still permitting students to express what they really want to say.
For more advanced students, you may want to gradually phase in a requirement that they first try to circumlocute to express the meaning they’re reaching for, before saying it in English. If you do, make sure circumlocution and the patterns your language requires to make that work are readily available. I start beginners with circumlocution signs on the wall from the beginning, so it’s not a sudden big deal when I start using them (well before I ask students to do so — no output without input first!) Just point, check comprehension (yes, even for advanced students… There’s time enough out in the real world for them to have to guess and wonder about new things) and go on with whatever you’re doing.
The use — not abuse — of English lowers the affective filter, builds community through better communication, and saves time, which we never have enough of. The magic of talking to your students about them is in the communication, from their point of view, since they aren’t thinking about the acquisition. Don’t break the spell by refusing to use English in a principled and responsible way.