[buildmaster5000]

I will assume this will actually happen, and leave the debate for another thread.

Go for laptops. REAL computers: Kids these days want computing power, and lots of it. Also, the more computing power, the more it will get used.
Go mobile: make sure there is a lot of battery life, or a plethora of outlets/chargers in every class room. It does no good to give out laptops that won't last through the day.
Expansion ports: 2 USBs is minimal, but more is always better
wifi b/g/n is a necessity. No questions.
If there is no internal optical drive, an external one is also required
Focus on upgradablility. Get something that is easily able to adopt new standards of RAM and SATA hard drives. Make sure that these things are easily accessible too.
Audio in/out is a good idea, but not required. Really just audio out is required.

As far as software: make sure that it can run windows 7, but run whatever OS the school system uses. I would not put monitoring software on it, but retain the ability to search the web history etc if there is a reason to. Having Microsoft office is also required, just because its the industry standard.
Finally, give the kids admin rights. Its so frustrating for me to get onto a computer that cannot run software because something like java is out of date. The kids need to be able to upgrade/install stuff.

I would also throw out the idea that including an image disk, with the appropriate disclaimer is a good idea too. Either way, reimage the computers each summer to keep them relatively functional.