OLPC's founder Nicholas Negroponte discusses educational use of the tablet form factor followed by a discussion with Marvell's co-founder Weili Dai. They are building the $75 XO-3 Tablet for education, to be showcased as prototype within 3 months by next CES. Possibly that the first prototypes may even get to be using the latest wide-view capacitive Pixel Qi LCD screens and the Marvell Armada 628 processor.
To be productive using a tablet, I think plugging a $2 USB keyboard and mouse could still be the best solution. As text entry can hardly be as fast on a tablet, even using haptic feedback or web based voice recognition technology. If the USB keyboard/mouse can be developed to cost $2-3 maximum, then I think it would make sense to provide each child with the $75 tablet and the $2-3 keyboard/mouse combo as well as some kind of cheap bag that holds them together or perhaps even better, the keyboard/touchpad could double as a thin, cheap and light screen protector for the tablet when carrying it around and could as well be clipped onto the back of the tablet when only using the tablet mode.
Filmed at the Mobilize conference organized by gigaom: http://gigaom.com/2010/09/30/mobilize-2010-negroponte-sees-tablets-as-creative-tool/