Why did the Greeks strive to ensure that children receive a decent upbringing and education?

In ancient Greece, citizens strove to ensure that their children received a better education. The reason is that democracy rules in Greece, and each person could achieve high results in science, art, politics, trade and other areas thanks to his mind and work, that is, due to personal qualities and education. At the same time, in Greece, they did not pay attention to the estate position, the main thing was that a person is a citizen of a country or a policy. Education was required so that the child in the future could serve his homeland and benefit.