If you are, like some schools, using social networking with your students, Facebook fan pages may be a better way to go than "friending" your students. Having students as fans rather than friends means you have more control over the interactions and you can't see their status updates, or in fact any of their private information.
Of course a Ning or even a Moodle would probably be a better idea for online social network-style interactions with students, but that would mean another login for them and for you. These are also less likely to be blocked by your school district's network policies. This is still relatively uncharted territory, though, so it is recommended that you proceed with caution.