What Benjammin said. Those were excellent points.

I don't have kids of my own yet but I can relate my chidlhood experience. Even though I grew up in the city, my dad (who was raised on a farm) introduced me to the outdoors at a pretty young age. He gave me my first knife, his old Mora, when I was 6 or 7. A few years later I also got to learn how to use an axe and billhook. Of course, I already had the chance of observing my dad at work much earlier so it was very much a natural progress. I believe that's how it used to be done in the past, at least in the countryside. It is a pretty good method IMHO.

I guess I was more responsible at my age than most other kids and I never abused my knives. Somehow my dad made me understand that a knife is foremost a tool, nothing mystical or awesome about it. And as any other tool, you need to master it gradually. Even before he let me keep that Mora he would often whittle a stick and show me how to do some simple carving, then I could give it a try myself. After a while I was simply allowed to keep the knife, take care of it (I was also taught how to sharpen it) and that was that. All very natural and probably the reason I never felt the need to show off in class, bring a knife to school or do anything stupid with it.

Not sure if that helps but I suppose you can only answer the question yourself as a parent. Hopefully you know your son well enough. If you already spend a lot of time outdoors with your family and if he is mature and responsible he might already be entrusted with a sharp blade. Or better yet, just allow him to handle a knife occasionally, teach him how to use it properly and look at whether he tries to abuse it in any way. If he does, he is obviously not ready yet.