I teach high school chemistry and physics in a low income area, all of my students are always on social media. Maybe it's because I'm in my mid twenties and I grew up with social media myself, but I have no problem interacting with them there. When I'm not teaching, I'm pretty much always on my phone myself.
I have countless students and former students who have me as Facebook friends and who follow me on Twitter and IG. I mostly post pictures with family and friends, science articles and bodybuilding / fitness / nutrition stuff. My students often send me private messages to ask me questions about homework, exam content, concepts we saw in class, etc., because they know I always reply right away and I'm pretty easy to talk to. Sometimes they also talk to me about more serious things, like bullying, issues at home or mental health issues. They say that it's easier to chat with me than to talk about it in person.
I don't think the school administration is aware that I'm doing that, but I've been doing it for a few years, since I started working there actually, and I've never had any kind of trouble with anyone. It's not like I'm doing anything wrong. I genuinely want to help my students as much as I can, including outside of the classroom. Like I said, I think HS teachers should have that kind of openness with their students. Adolescence is a crazy period for most people, the last thing these teens need is stupid policies getting in the way of their interactions with other human beings who are willing to help them.