The article explicitly mentions that students use an app called Remind. I would not call this, along with the web portal etc, social media per se, but it does approximately fulfill the ISocialMedia interface.
I think there's an important distinction. Social media are by definition social, so what happens there is public.
Getting your marks sent to you when you are in a different context is private; you can feel shame or stress and in fact not know how you rank vs your peers.
The social stress isn't that new, and as far as marks went both my parents grew up under systems where the marks were posted outside the classroom and class ranking was also public.
I was really struck about the "prepared" part -- a lot of this should be considered spam: I don't need to know my marks (or bank balance etc) in realtime; I want to be able to get that info when I am ready to ask for it. The continual barrage of requests for attention is itself stressful. Having access to uninterrupted quiet (and boredom, especially for younger kids) is important for mental health and creativity.
Social has its own positive place as well. HN is a form of that.
Sorry, I don't mean "public" in the sense of "universally accessible".
I'm using the sociological sense where "private" means "to one's self" and "social" or "public" mean "part of a common experience or utterance with at least one other person" because I think that's the important distinction in this thread.