Our local schools have very strict standards on donated PC's because of maintenance costs. They don't want to become a dumping ground for old computers and spend lots of money trying to keep them running.
It costs less than $300 to build a good computer so resale values aren't very good on old ones.
Yep, but the oldies are good for young kids to play with. A good learning experience. Probably learn more just trying to repair them... a cheap technical indoctrination, IMHO. (learn about electronics, basic computer structure, can open up drives/floppies to study mechanisms, etc.) Somewhere around here I have an old 8088 chip cut-open and encased in clear lucite. Children are sponges. Inquiring minds want to know.
my 2¢