Microsoft
Microsoft has already taken some potshots at Google's Chromebooks in the past -- Windows 8.1 with Bing, anyone? Now, though, it's going for the jugular. The newly introduced Windows 10 S (not Cloud like the rumors suggested) is a stripped-back, education-oriented version of the operating system that gives up some app support in the name of simplicity and performance. You can only run Windows Store apps (including Office 365 apps, which are coming soon), but that's the point -- schools don't have to worry about the vulnerabilities that come with running any old Windows app. Store apps run in a relatively safe container where malware and other threats aren't likely to be an issue.
It also includes tools to help teachers manage their PCs, such as the ability to easily preload software using a USB key. And while it's separate from Windows 10 S proper, there will be a classroom experience for Microsoft Teams that lets teachers and students chat and collaborate.
Windows 10 S will be ready in the summer, and it's clear that cost will be important: PCs shipping with the operating system will start at prices as low as $189. That's not too far off from the previous floor for new Windows PCs, but it's definitely competitive with Chromebooks. There will be perks beyond the low price, too. Microsoft is promising a year of free access to Minecraft Education Edition as well as Office 365 for Education with Microsoft Teams. Also, schools running Pro editions of Windows in the classroom can move to Windows 10 S for free -- if they're not worried about running non-Store apps, they can move to a newer platform at no cost.
Check out all the news from the MicrosoftEDU event here.