USB-wired Ethernet means reverse tethering. Unfortunately, it really isn't practical on a classroom scale, because of the distances involved, not to mention that general-purpose computers aren't really all that great at handling high-speed network routing for thirty or forty machines to begin with, and USB's excessive CPU overhead just piles on top of that.
It would be cheaper and more reliable to install a dedicated Wi-Fi hot spot in every classroom with a fairly directional antenna on the ceiling, and set the maximum transmit power really low so each classroom acts like its own microcell that is roughly limited to the bounds of the room. Chances are, a single shared Wi-Fi connection is plenty fast enough for a single classroom, and in my experience, as long as you aren't doing tethering, Wi-FI works very well on iOS (the recent WPA2 Enterprise networking authentication changes in iOS 8 notwithstanding). It's only a nightmare on Windows, which is probably one of the reasons that Microsoft is getting stomped into the ground in school markets.... But I digress.
BTW, does anybody else find it odd for an article to say that MS is losing the market? Normally "-ing" verbs imply that something is happening right now. I was under the impression that they had pretty much lost the K-12 market to iPads years ago.