Chinuch Hora'ah of the Day:
Even when a child is small and not able yet to grasp the meaning of Torah and kedushah, he can already sense that his home is different from other homes, and thus he is automatically not influenced by other children. On the contrary, when he sees other children not behaving properly... this in itself makes it very clear to him that he will not behave this way and he knows that he should not become friends with them.
... When a Jewish child is taught while he is still young to know that he is different from all of the other children in the world, then also later, when he grows older, he will remain uninfluenced by others his age. But rather, he will go away just like his forefather, Yaakov, learning only Hashem’s Torah. He will speak in a manner of هملّْ لي (“You shall speak of them” [words of Torah) until even his mundane speech includes only words of Torah. And just like Yaakov, when he matures and gets married, goes into the world, builds a family, and has the yoke of parnassah on his shoulders, then too he will establish set times to learn Torah every day, as did Yaakov Avinu. When he is involved in material matters, he will say Shir Hamaalos and have complete bitachon in Hashem, and automatically his whole business conduct will be only according to Torah.
(Likkutei Sichos, vol. 3, pp. 792-794)