First - the site: I love the simplicity. The concept is clear immediately.

Second - the service itself: it's a great angle. Kids love SMS messages and this embraces the use of technology/cell phones in a positive way. It creates a more personal connection between teachers and kids without breaching privacy. We had something similar, though far more basic, when we were working on an LMS and that was a highlight we often overlooked but got the most vibrant response.

Great work so far!