If I had a pound for every head teacher who said they were worried about using the leading social media platforms "Twitter" and "Facebook" I think I would have £45.00, or perhaps more. The main fears are that, let's call them, 'certain users' will take advantage of the ability to publically post comments as a way to complain or, even worse, be abusive or threatening toward the school or its staff. From experience, such behaviour is rare but when it does happen the implications for the school can be significant, calling up all manner of policies like complaints, greivances, acceptable use,  safeguarding and more.