The Republic by Plato Part 7 Page 74

were no danger they were to be brought close up and, like young hounds, have a taste of blood given them?

Yes, I remember.

The same practice may be followed, I said, in all these things — labours, lessons, dangers — and he who is most at home in all of them ought to be enrolled in a select number.

At what age?

At the age when the necessary gymnastics are over: the period whether of two or three years which passes in this sort of training is useless for any other purpose; for sleep and exercise are unpropitious to learning; and the trial of who is first in gymnastic exercises is one of the most important tests to which our youth are subjected.

Certainly, he replied.