From a language teachers’ mailing list:
I am a Level 1 teacher in an IB middle school…each unit needs to have “Inquiry Questions” outlined of 3 types- Factual, Conceptual and Debatable…my students are operating at a pretty low level when it comes to communication…I feel like sometimes my program is a square peg trying to squeeze through a round hole.
A couple of comments:
1. ANY question that asks Why? is a higher order thinking question.
2. ANY question that involves speculation of a future result is a higher order thinking question. (“What do you think will happen next?”
This from my experience teaching the story of Cinderella in Chinese and being criticized for not asking more higher-order-thinking questions.
This post ( from around that time may be of some help if you need “ammunition”.
3. The flipped classroom is your friend (getting this sort of thing out of your input time, but also looking really “modern” and “cutting-edge”). Well, not a truly flipped classroom (not time outside of class preparing for time in class) but at least a model where the English-based Great Questions are largely handled outside of class.
And, of course,  (it must have been proven that) posting Essential Questions on the wall is enough to have them function to improve classes — that is required in so many places. Maybe just posting some of these questions on the wall and keeping your class in the target language would be “enough”.
Can you set up a Web site for your kids? If you can set up something that has a discussion or comment feature, you can post questions and have them discuss that way. Many “respectable” (?) online classes require a certain number of posts to a discussion forum as a part of class work (these are actually college and graduate level). Granted these institutions are not all, ahem, top-tier, but they grant tertiary degrees, so surely doing something like that for a high school course should be sufficient.
Failing that, can you assign these Great Questions to small groups of kids, and have them research them on their own and come back and give a report in English (if necessary)? Then do a quick vote, or something, and go on with input. Covered! (Are they expecting an essay about these things on the final? Then it will take a review game the week before, maybe a Jeopardy game or something, to review these Crucial Big Concepts.)
I always petulantly wonder in these cases how much time is being taken up in math and history classes asking intricate questions about the historical development of the verbal system in my target language, since I evidently have to take up my time to consider questions that belong in History/Social Studies or whatever, that my kids are not yet ready to discuss in the target language.
The whole ab initio IB program is, IMHO, unrealistic. Or rather, it’s über-traditional. It yields a typical bell curve. The basic problem is that TPRS/CI is a mastery method, and everything else is not. The best you get with any other method is “we hope most of them got most of it”. Not “we expect almost all of them will get almost all of it”. IB isn’t about being able to speak a language, IMO; it’s about being “rigorous”. Don’t even get me going.