Google Chromebook VP Caesar Sengupta Business Insider/Julie Bort In the war over who owns the future of the PC, there is one super important battleground: schools.

Kids that grow up using a particular flavor of tech tend to take it with them into the workforce.

That's why Microsoft offers schools all kinds of discounts and both Microsoft and Google give schools free access to their respective clouds, Office 365 and Google Apps.

That's also why this is a statistic that should deeply scare Microsoft: About 22% of the school districts in the U.S. are now using Google Chromebooks. That's over 5,000 K-12 schools, Caesar Sengupta, vice president of product management for Chromebooks told Business Insider. (Sengupta was one of the original Chromebook team members, starting it in his free time as a "20-percent" project.)

Chromebooks are the cloud-based notebooks that run Chrome OS as the operating system.

"We are heavily investing in Chromebooks," Sengupta told us. "There's two different segments we care a lot about: consumers ... and K-12 schools."

Sengupta is pleased with its progress so far with both groups. He points to a report by NPD Group from last week which says that in just a year, Chromebooks went from negligible share in the back-to-school PC market to 3%.

Google sold 175,000 units in the 10 weeks of June 30- Sept. 7, NPD analyst Stephen Baker found with Chromebooks providing "all the growth" in a lackluster market hurt by tablets. Overall PC sales declined 2.5% from the 2012 back-to-school period.

To be fair, Windows still sold the lion's share, commanding 58% of the market (compared to almost 61% in the year-ago period) and Macs held on to 20%, NPD says.

So Sengupta knows there's still work to do and he's working on it. HP, Toshiba, Acer, Asus all announced new Chromebooks last month using Intel's new Haswell chip, priced at about $300 and available for the holiday season. Haswell promises fast performance and very long battery life.