Incorporating a cyber safety curriculum into the classroom would be a great start http://www.commonsensemedia.org/educators/curriculum
This is the best K-12 cyber safety curriculum I have seen and dipped into. I have not introduced it as much as I would like to.
iSafe also offers a wide array of tips and ideas for addressing this issue, both as a parent and teacher. You can check it out here:http://www.isafe.org/channels/sub.php?ch=op&sub_id=media_cyber_...