Institutio Oratoria (1.3.11-1.3.13)

Such relaxation must not however be unlimited: otherwise the refusal to give a holiday will make boys hate their work, while excessive indulgence will accustom them to idleness. There are moreover certain games which have an educational value for boys, as for instance when they compete in posing each other with all kinds of questions which they ask turn and turn about.

Games too reveal character in the most natural way, at least that is so if the teacher will bear in mind that there is no child so young as to be unable to learn to distinguish between right and wrong, and that the character is best moulded, when it is still guiltless of deceit and most susceptible to instruction: for once a bad habit has become engrained, it is easier to break than bend.

There must be no delay, then, in warning a boy that his actions must be unselfish, honest, self-controlled, and we must never forget the words of Virgil,

So strong is custom formed in early years.

Georg. ii. 272.