Introduced at an early age to the written page by her father, Scout is certainly enriched through reading in her preschool years. For, Atticus does not embrace what he feels the people who run public education do. According to him, they
"promote the stupid and idle along with the industrious--because all men are created equal in the sense some would have us believe."
Instead, Atticus teaches his children at whatever age they are ready for new concepts--whether they are in the "proper" grade, or not. He introduces them also to new ways of thinking about things, such as telling Scout that she needs to consider things from others' points of view. As a result of this method of education for his children, the Finch children's thinking is much more expansive than that of others of their age groups.
In addition, Atticus teaches his children many a lesson that is not in any textbook. And, he teaches by example. For, instance, he has Jem read to Mrs. Dubose, and Jem witnesses his great shooting as he kills a rabid dog.