There are many different places to Blog. For teachers and learners here are a few blog sites you can get set up on. These blog sites have features that lend themselves to schools.
21Classes ( This one is free for a basic account. If you want access to more features, you pay a fee. )
edublogs Edublogs.org is a site specifically for teachers, students, librarians, researchers, professors, administrators, corporate trainers and anyone else involved in education. I find it interesting to note that this tool is Currently powering 225,294 blogs.
Blogger.com This is the one you are viewing right now. It has some really useful features and templates.
If you are interested in setting up a blog, I suggest exploring some of these links to determine what sort of blogging service would be most useful for the blog site you would like to set up.