I have kids in school with school issued iPad Air's. I can see why some school districts want the cheaper Chromebook instead. Many of the education software on the iPads were repackaged, older Flash content, they don't work very well on the iPad and crashes a lot.
But I still don't trust IDC numbers. For all we know, the Chromebook were purchased to replace netbooks and laptops. Also this is the same IDC that predicted Windows phone to dominate by 2014.