The percentage of a countries people who can read and write?

only the rich

That is not true. Europe, North America and several other parts of the world have free mandatory school attendance for a certain number of years and thus have a high rate of literacy. Some countries have no money to provide schooling. In some countries education is only available to those with money. In some countries education is denied to certain elements in society, notably women. In some cultures education is seen as just causing trouble; if you are going to be a farmer, geometry or philosophy is not going to be much practical use.

But many farm boys and girls have gone on to make great contributions to their societies and nations.

A general education including history and science is priceless in itself.