Youth Change Workshops (http://www.youthchg.com) has cyber-safety posters to help you address this difficult issue that invades your school and classroom.
Students need to understand the ramifications of their online behavior. That's hard to teach to elementary, middle or high school students who don't have much of a perspective on the topic. Posters like #276 can help deliver your message better than plain spoken words.
Teach your students about how to behave online on the internet, and when using electronic devices, then let Poster #276 reinforce your message by providing an on-going reminder. It's much harder to misbehave or engage in questionable behavior when a warning poster like #276 is staring down at you. So get Poster #276 on your school or classroom wall now.