Are Rules Futile or Helpful?

A person is not born as a virtuous person. I think that Ariston agrees with this statement. Learning the principle of moral philosophy, discovering the appropriate rules and internalizing them is a long process which require biological growth, analytical brain and time. Hence, how can Ariston expect from a four year old Yahya (my son) to learn by his mere reasoning not to bite his sister? Rules and sanctions are necessary to protect the virtuous people and their daughters from the harms of irrational actions of immature creatures, like Yahya.