This man did actually teach his boys righteousness in the way you suggest, to lie and not to lie, to cheat and not to cheat, to calumniate and not to calumniate, to be grasping and not grasping.

He drew the distinction between our duty to friends and our duty to enemies; and he went further still; he taught men that it was just and right to deceive even a friend for his own good, or steal his property.

[32] And with this he must needs teach his pupils to practise on one another what he taught them, just as the people of Hellas, we are told, teach lads in the wrestling-school to fence and to feint, and train them by their practice with one another.
Now some of his scholars showed such excellent aptitudes for deception and overreaching, and perhaps no lack of taste for common money-making, that they did not even spare their friends, but used their arts on them.
[33] And so an unwritten law was framed by which we still abide, bidding us teach our children as we teach our servants, simply and solely not to lie, and not to cheat, and not to covert, and if they did otherwise to punish them, hoping to make them humane and law-abiding citizens.

[34] But when they came to manhood, as you have come, then, it seemed, the risk was over, and it would be time to teach them what is lawful against our enemies.

For at your age we do not believe you will break out into savagery against your fellows with whom you have been knit together since childhood in ties of friendship and respect.