First post, by ElectricMonk
I recently came into several older PCs (nothing vintage) that were barely suitable to run Windows XP, let alone do anything neat. So, I decided to re-purpose them as an educational machine for kids.
I ended up selecting Ubermix as the OS, since:
A) It's Ubuntu based (it is vulnerable to Shellshock at the moment, so it'll need bash to be patched)
B) It was designed with education and older PCs in mind (It does require 1GB ram, though)
C) It comes with tons of neat educational resources, games, Libre Office, Scribus, and even programming tools to get kids interested in programming
D) The userspace is completely separate from the base OS, so if the kid borks his userspace, it won't crater the entire OS. Just insert his/her thumbdrive, and fix it 5 minutes.
E) The UI is designed to resemble a smartphone, to make it easier for kids to learn how to use it.
If you want to test it out before installing it to an older PC you've got laying about, install Oracle's Virtualbox and the extensions on your main rig, then download the Ubermix 2 ova file, and use the Vbox manager to import that ova file as an appliance, and then you can check out everything Ubermix has to offer, while it's running in a VM.
*EDIT*
I failed to point out that each kid will need his/her own 4GB thumbdrive, since that's used for their userspace info, as well as saving their homework/documents to.
*side note*
I've been able to successfully use Ubermix, Xubuntu, Mint 17, Haiku, XP Pro, Win2K8R2, OS X Mountain Lion, NT4, Netware 5.1, and OpenSolaris 11 in Vbox for use in my GNS3 simulations. If you need a hand, I can probably help out.