When we read the verse (from the "Shema'"): "You shall teach them to your children and you shall speak of them..." (Deuteronomy 6:7) we may question why the first you ("Attem") is in the plural, while the second one is written in the singular form ("Atta").
The answer is that when we want to teach our children something, we, as individuals, must first teach ourselves that which we would like to transmit to our children, so that we can be their role models.
Hakham Yoseph Hayyim, 'a"h, the Ben Ish Hai, relates a story about a father who saw his son eating bread without first washing his hands (Netilah Yadayim). The father wanted to impress upon his son the importance of this Miswah. He decided to teach him a lesson and hit him with a stick. He held the stick in one of his hands and his son's both feet with the other hand. When he lifted up the stick to hit his son's feet, he missed. Instead he hit his own hands!
The son turned to his father and said: "You wanted to hit me for not washing my hands, but you yourself never make Netilath Yadayim. This is a message from Heaven saying: 'Why hit your son? Hit your own hands for not washing!' Since I have never seen you wash your hands, I never bothered doing it myself".