A question of high importance in any investigation of ethics is how we can teach people to be good. Aristotle is quite clear that he does not think virtue can be taught in a classroom or by means of argument. His Ethics, then, is not designed to make people good, but rather to explain what is good, why it is good, and how we might set about building societies and institutions that might inculcate this goodness.
According to Aristotle, virtue is something learned through constant practice that begins at a young age. We might understand his outlook better if we recognize the meaning of the word arete, which is rendered as “virtue” in most English translations. This term more generally means “excellence,” so a good horseman can exhibit arete in horsemanship without necessarily implying any sort of moral worth in the horseman. It should be obvious to anyone that excellence in horsemanship cannot be learned simply by reading about horsemanship and hearing reasoned arguments for how best to handle a horse. Becoming a good horseman requires steady practice: one learns to handle a horse by spending a lot of time riding horses.
For Aristotle, there is no essential distinction between the kind of excellence that marks a good horseman and the kind of excellence that marks a good person generally. Both kinds of excellence require practice first and theoretical study second, so the teaching of virtue can be only of secondary importance after the actual practice of it.