Paideia: The ideals of Greek culture, by W. Jaeger.
Education in Homeric times, by H. I. Marrou.
The pedagogical revolution of the early Sophists, by H. I. Marrou.
History of the Peloponnesian War, by Thucydides.
The clouds, by Aristophanes.
The frogs, by Aristophanes.
Nichomachean ethics, by Aristotle.