If you are fearful of Facebook and MySpace then you need to create an Edmodo account. Edmodo was designed specifically for educational purposes. You must be a teacher, student, or parent to gain access. It allows you all the amenities of those other social networking sites but with a lot more security/privacy.
Yes, it is free and you can manage student accounts. It is only open to those you invite in and only educators may obtain an account. You may monitor and moderate all conversations, administer quizes, embed media, etc. The groups feature is very effective and you may grant access to your group to other classes. We just had 700+ students interacting in a global collaboration project, Digiteen.
Students do not need an email address to use Edmodo, so under 13 is OK for CIPA. It looks much like Facebook, so kids love it and parents need some education on it as they fear it at first. Parents can get monitoring access so they may monitor their child's activity. It is a great tool to show parents how social media is used in education.