Why did the Greeks call the theater a school for adults?

Theater in ancient Greece was called a school for adults because in fact it was an educational institution. At the performances, the audience learned a lot of new things for themselves, they learned to be patriots and citizens of their country on the tragedies of Sophocles, Euripides, Aeschylus. The authors of the tragedies used mythological motives, but this outer shell meant the problems of modern life, philosophical and ethical questions were raised. The Greeks loved to watch comedies that ridiculed various unsightly aspects of social and political life.