Four or five years ago I took my daughter to the Trenton Computer Festival. (it's just a shadow of it's former self, thanks largely to the internet, I suspect.) She wanted to use her own money to buy her own computer.
We found an ancient Compaq Pressario laptop -- I believe it dated from 1999 or 2000. It had a 6 GB hard drive. The dealer plugged it in to show that it worked. I can't remember the price -- it was cheap. (I gave her a new battery for it -- cost more than the computer.)
Anyway, we found a distro called
wattOS. It's a very lightweight Linux and was very, very usable on that ancient PC. She had a word processor and spreadsheet for school and, with a $5 USB wi-fi dongle, she was on Facebook.
Just another "small" Linux to consider.