I briefly worked with international students doing a pre-university course. Most were 18 or more, a few were 20 or more, but a few were 17. As such we had a degree of pastoral responsibility for them
I made a blanket rule of not friending students from there. Even though neither I nor the students are still associated with that college, I still don't.
However, one of my colleagues uses FB for class discussions and sharing information. She has on one occasion busted a student who claimed to have missed a test due to stomach illness, when they posted photos of the big steak they had for lunch.
