Such questions are on-topic.
For example there has been the meta discussion Are questions about teaching writing on-topic?. Not much "discussion", but no single downvote on the question and answer. It's the only discussion I could find, so nothing that would point towards not allowing this topic.
The Help Center, specifically the page What topics can I ask about here? says:
If you have questions about writing techniques, style, usability/readability, planning and organizing, research techniques, publishing, and related topics, your questions are welcome here.
Teaching "writing" is definitely related. It's also nowhere in the no-no categories.
I couldn't find a whole lot of questions on the main site about teaching. One example is On writing an essay, what are some good techniques to teach to schoolchildren?, which seems to be the closest to what you are asking. This was well-received at the time.
Another example would be Should IKEA assembly instructions be used as positive examples to train technical writers?, which is relatively recent when compared with the other example and was also well-received.
Another thing to keep in mind is that a question is not off-topic just because it could be on-topic somewhere else. I am not completely sure if Workplace or Academia would accept such questions, but even if they did this is no reason to deem them off-topic here. While it's good to think about how we differentiate this site from other sites on the network we should judge questions based on how they fit our scope. And I don't see anything in our current scope definition that would say that such questions are off-topic.
All in all I'd say that such questions are on-topic and should be encouraged. I think they are valuable for people learning about the topics and for people teaching the topics. More expert knowledge surrounding everything related to writing is good for the site. This is a place to exchange knowledge about writing after all.