Students not seeing friends
My students aren't seeing friends or friend lists or the activity of friends and they can't message them. What's going on?
Hmmm. There's a poorly-thought-through A/B test going on at the moment - Duolingo are experimenting with getting rid of activity streams. As a short-term work around, your students will be able to see their own and each others' activity streams if they log out, or use a private browsing / incognito window.
Duolingo isn't really designed for communication. Assuming your school has a VLE, you might want to set something up for your class on your course page.