So what happens when a 7th grade girl goes to a party, gets drunk, gets date raped by 6 guys and Mom and Dad's lawyer is saying it's because of the people she met using her school laptop and the local DA is saying you're not just responsible, you're criminally negligent and only jail time will send the right message (it's for the children, you know.) . . . you get the idea, it won't be the "information wants to be free" folks on Slashdot judging you. You're facing a liability nightmare unless you're filtering social networking sites and blocking chat, irc, muds, and on and on . . .

As 87 people have already said, once one kid running linux at home figures out how to run a proxy and he makes accounts for half the school, your filtering becomes pretty pointless. Have you all asked a lawyer what liability the district would still retain?

Another thought: if a student checks out something expensive for an elective class and he breaks it, loses it, whatever, you can make him pay for it. If the school makes laptops a required part of the curriculum, on the other hand, you'll have a lot less leverage trying to collect money for damaged and lost equipment.

Your teachers are going into this transition with eyes open and know that getting students to pay more attention to a teacher than a laptop is essentially impossible, ya?

Seriously, you'll be facing a quagmire of liability issues, repair costs, and pedagogical problems.