Edublogs is a blogging platform that is quite popular with educators. Edublogs provides services for individuals, for classrooms, and for entire school systems. Edublogs Campus is the service for classrooms and school systems that allows teachers to manage the blogs their students create. Edublogs Campus is normally a fee-based service, but right now they are making a nice free offer. Right now you can sign up for Edublogs Campus and use it for free for a semester with no strings attached. Learn more here.
For those people who are interested in individual Edublogs accounts, the free version of Edublogs inserts ads into your blog. For $40/year edublogs removes those advertisements.