I don’t know too much about distros, but you want something quite light. Let’s be real, enterprise like schools won’t pony up everything for Debian, especially when they just use Chromium and maybe Libreoffice. Schools are cheap, and if you can hacksaw together an Arch-based thing, they WILL buy miserable hardware, that can just barely run it, and an 8 gig SSD is much more stomachable for them than a 32-gig for Debian. SteamOS doesn’t completely crash, and that’s infinitely more complicated. This is basic Arch, plus a WM, plus Firefox/Chromium/Whatever.

You could probably make a small Arch install, add LibreOffice and something either like the GNOME browser or Firefox. What people using ChromeOS want is something light (for cheaping out on hardware to schools), and basically just a way to access a browser. Plus, something something permissions. ChromeOS is marketed towards enterprise, like education. Just need the bare minimum to get on the 'net, and no more.