This is a good article with a lot of resources for teaching Digital Citizenship in the classroom. One philosophy I endorse is to integrate Digital Citizenship into class lessons, not teaching these skills as a lesson in itself. Students learn better with a purpose. For example, students are told to demonstrate digital citizenship in an online discussion forum related to subject matter taught in the class.
If you haven't yet checked out Google's "Be Internet Awesome" I would highly recommend it.
This is a great resource to help guide students and staff to not only promote digital citizenship, but get everyone on the same page with terminology and meanings. It is a great way to get parents involved as well.