The link for an example of a classroom blog space can be found here.
WordPress has so many great things that come with the free version (wordpress.COM) for a classroom blog to be functional. As you can see in my example, you can embed Google .doc files that will update on the page when you update the original document (see: Book Club), or Google calenders that can be set up for the class and updated via Google as well (see: Upcoming Events). Sidebar Widgets are great little add-ons that you can customize by activating. Here I have chosen to put contact information, RSS feed for the parent or student on the go, and a class chat room available through tlk.io. To use simply activate the widget, go to the website, and make sure that the Channel you create on the website is the same one in the widget details.
If you are wanting to do more customization, you will have to sign up for a wordpress.ORG website that supports the use of plug-ins.
This web blog is public, but WordPress has the options to make it private where you can invite people to join. Simply go to Settings>Reading and you can set up privacy preferences for your class.