21 Classes is one of my favorite blogging solutions for schools. This free site allows teachers to create student accounts (no email necessary) to post (up to 10). Also, there is a paid ($8.95 a mo) classroom package which allows schools to create a blog portal. This allows up to a 100 students to blog while teachers have control over what gets posted or if comments are allowed.
I highly recommend checking out 21 Classes by clicking here!!!