Actually, when this story by Futuresource first came out, it was a lot of fun to debunk. As mentioned by someone else, this is also new sales, not existing devices. But that's not the best part. It excludes desktop computers, which is pretty much the primary form of computing device bought by schools.

The claim that it's "50% of personal computer sales" in schools is completely false.

http://www.cnbc.com/2015/12/03/googles-chromebooks-make-up-h... <- The word "sold" was added to this headline after I pointed out sales figures and devices in classrooms were not the same thing. I am still annoyed they didn't add in the world mobile. Apparently desktops aren't "devices" anymore?