I have owned and carried a knife since the age of 5 when my father gave me my first pocket knife. At the age of seven I received my first 6" fixed blade clip point. I remember using a knife for skinning, cleaning small game, and helping father sharpen his knives from a very young age. Knives are a part of our lives, probably everyone of us have several knives in our home in arms reach of our children; like in the kitchen. Defense is about learning and doing what one must do to protect ourselves, our families, our property. Children need to know and understand knife safety. They are sharp and teach what that means, they are pointed and piercing and teach what that means. Teach how to handle knives safety. As to training defense against a knife, teach defense movements and positions against empty hands as though there was a knife. Teach the attributes, principles, and positions as though the knife were actually there. As the child grows, matures mentally introduce the concepts of the knife with a markers continueing the teachings of proper knife safety and a strong emphasis on not getting touched by the marker due to major damage. It can be taught slowly, safely, and responsibly with some kind of reality. Now as to teaching the using a knife for attacking in a defensive situation I hold for much older and mature teens.