Childnet has produced a short information booklet aimed at teachers and support staff in schools. It outlines how best to use social media services in both a professional and a personal capacity.
The document covers areas such as privacy settings, professional reputation and how to respond to friend requests from members of the school community. It also outlines a number of common scenarios with guidance on how to deal with them.
You can find the guide here: http://www.childnet.com/ufiles/Social-Media-Guide-teachers-and-support-staff1.pdf