I have a 8 schools set up in the game, and the are always fully staffed. The Population is 475/47/54. I have had less population, and still the same results. However, I can't seem to get past about 72% educated in my 200-300 person city. Will more schools help, or do I need to do something different?
Only children can be educated, once someone becomes an uneducated adult, they remain uneducated until they die.
Eight staffed schools will be able to educate 160 students simultaneously, so should serve your youngsters well for the immediate future, as your older workers die off you should see your education percentage rise.
There are a few challenges to attaining a 100% education rate in Banished.
1) You must have school capacity greater than your maximum number of children. If you fill up and one slips through, it will take a long time for that one adult to die off to attain 100%.
2) You must make sure you never let a teacher die without a replacement. The students who are enrolled at the time will be expelled and not be marked as educated, as they have no teacher to teach them (essentially, the capacity decreases).
3) Don't accept nomads. Nomads are uneducated and include adults, who can't be educated.
4) Time. You'll need to wait for nearly complete turnover of your population, or at least until the last uneducated person dies off. Since it's difficult to identify and kill off the uneducated, the foolproof way is to simply wait them out.