A bit outdated but good overview of social media safety tips for parents (but applicable to teachers too). Also outlines age minimums for accounts on the most popular site (Facebook=13, Twitter=none, etc)
The Internet is an integral part of student life. It is how most students study, communicate and research everyday. Though the web often makes student life more efficient, those digital footprints may put personal information at risk if the right precautions are not taken. The following is a useful (and relatively quick!) guide to keeping students safe online