I developed and used these two documents: (1) a letter to parents, and (2) an Acceptable Use Policy for 8th graders to obtain and use personal Google accounts for school (primarily g-mail and docs) related communication and collaboration.
A few notes:
-Though the documents refer to Google accounts, they could easily be revised to promote internet safety for any interactive web tool.
-I purposely wrote the documents so they would apply to "school-wide" use, though students primarily used the tools in my language arts and social studies classes.
-Developing and sharing the documents with administrators, peers, and parents was a great way to get buy-in. You might do the same, using these as drafts for feedback and revising to meet the needs of your school setting.
-The rule the students broke (most frequently) was using the tools under another student's name - usually nothing nefarious, but the "innocent" instances became great teaching tools for what else could go wrong.
-The hardest to monitor was if they used their accounts for other purposes - I know they did, but there was never any real need to police it unless something went wrong, and there was the policy to fall back on.
Thanks for your interest!