My brother is a secondary school teacher, and at one point would fairly often get friend requests from his pupils.

I thought this a little odd. So did he. But in the end he figured out which box to tick so that they could be his friend, without actually letting them see anything, and this seemed to keep everybody happy.

(The subject hasn't come up recently so I don't know whether this is still the case, or whether his pupils have moved on to some other system, probably one that I've never heard of.)