Our school's laptop policy is still being tweaked and revised, evolving in light of experience.
I was interested to read Will Richardson's take on school computer policies on Weblogg-ed. Make sure you read the comments, too.
As a significant architect of our school's policy - not its final arbiter, but a carpenter creating a structure - one focus was to put things in positive terms, wherever possible. One does not of course want to discourage students from using their laptops - instead, fuelling and directing their enthusiasm is a great educational opportunity. On the other hand, the reality of life in schools is that it's important that students are aware of the necessary boundaries, such as respecting copyright, and treating other people respectfully.
So ours is still a work in progress. Feedback from the students has been positive - they appreciate clarity, because it's calmed some fears they had, from gossip/chat, about what might happen if...