Humphrey at Quodlibeta mentioned early modern courtesy books. Here's a useful admonition for teachers, from the most famous of the English courtesy books, Henry Peacham's Compleat Gentleman:
Peacham's Compleat gentleman, 1634 By Henry Peacham, George Stuart Gordon
Peacham goes on to castigate the opposing error of managing your students "so that every day is play-day with them". He has some amusing stories; for instance, the teacher that swore heavily while beating his students, which he did whenever they swore.
He gives salutary advice for how parents should manage the education of their children, as well.
ADDED LATER: Somehow or other I had completely missed the nention of Socrates. The reference, of course, is to the Myth of Theuth in the Phaedrus.