At my kids' school, they encourage appropriate cell phone use in the school. For example, if there is a homework assignment on the board, rather than wait for everybody to copy it down, kids are told to take a picture of the board. They also insist on the kids using some kind of calendar to track everything and most kids use their phone calendar.

There's some kind of Twitter-like service that is used for teacher-student communication and of course they use email and Google Docs a lot.

My kids have had assignments that involve making a movie and their phone is their video camera.

If the kids want to use a computer, they can (they are all issued ThinkPads that are frankly awful) but I think most kids would prefer to use their phones when they can.

Also, the school has a pretty aggressive filter on the wifi so kids that want to access the internet in the school end up using their phone to get access to the things they need.