Book III is where you will find large discourses on proper education, but here is a concise summary:
"Its central concern is an emphasis on achieving the proper balance of many disparate components—physical training and musical performance along with basic intellectual development.
One notable feature of this method of raising children is Plato's demand for strict censorship of literary materials, especially poetry and drama. He argued that early absorption in fictional accounts can dull an person's ability to make accurate judgments regarding matters of fact and that excessive participation in dramatic recitations might encourage some people to emulate the worst behavior of the tragic heros (Republic 395c). Worst of all, excessive attention to fictional contexts may lead to a kind of self-deception in which individuals are ignorant of the truth about their own natures as human beings. (Republic 382b). Thus, on Plato's view, it is vital for a society to exercise strict control over the content of everything that children read, see, or hear."