I think it should be up to the students and teachers if they want their students or teachers following them on facebook or other social networks. I personally think not because then you have teachers or students in your personal buisness. Its really just up to them if they want to let them follow them.
              If teachers were following students and students were following teachers then they all would be up in all of their personal buisness. Thats ok if you don't mind people in your buisness. If something were to happen or be said then you have younger and older people seeing it then there are some people that gossip and then it spreads and becomes a big fat mess.
               If teachers were NOT following students and students were NOT following teachers then people would not cause trouble because they know no one in authority would see it or so they think.  They know they wouldn't get their parents invovled because most people won't say anything. This is my conculision of teachers and students interacting.