Once upon a time reading and writing was only for a select few. Everyone else was too busy raising food and children, hunting for food, preparing food and clothing -- you know, the basic things that preserve life.
Once upon a time there were stories. Ah that’s the thing. Stories were what made life worth living. Stories were the passing of community information around and to the next generation. Stories were lessons learned and the good rewarded and the bad punished. Stories told in the evening once work was done. (Or they ran out of daylight.) Stories were entertainment for all and education for the young.
The storyteller was honored for his memory, and for his ability to create/ weave interesting tales, to choreograph call and response, and sometimes even to sing and lead the singing. It’s no wonder that, in Ann McCaffrey’s Dragonrider tales, Harpers were the educators of the young as well as those who passed along the news among the various settlements.
Just because writing was invented didn’t mean the end of stories and storytelling. It just meant that the best stories, the most important information, could be recorded for others -- those who would never get to see/hear the storyteller -- to enjoy.
But now children needed to learn to decipher those scratches upon clay, those pictographs on Papyrus rolls, those mushed together letters on parchment, those printing press letters upon paper. If life (creating food and clothing) was hard, then few could be spared to sit for the long periods of time needed to learn. But, as better methods of cultivation and weaving of cloth for clothing appeared, people had more time for education and books and reading.
But it still had to be taught. It still had to be learned.
We have no records of books written for children to read in the early civilizations. They might or might not have had them. During the Middle Ages, when life was more difficult again, only children of the upper classes were taught to read and write – mostly boys, but some girls. (Girls had more of the home arts to learn – spinning, weaving, embroidery, the making of medicines in the still room, the care of the home — clean rushes on the floor at least once a season— cooking, care of babies, etc. They often didn’t have time to simply sit and read.) And once children learned to read, they were expected to read adult books. The whole concept of a childhood was short – baby/ toddler/ youth – from age eight on they were expected to do their part with adults.
It was only after the industrial revolution that people extended the time of childhood to include the teen years. (Except for the children of the working class - who toiled in factories for 12 or more hours a day.)
Toward the beginning of the 20th century, the strange idea of limitation of child working hours and education for all took hold. Which sparked a demand for teachers and textbooks. And free libraries.