That can be a little tricky. Because each kid is different, the real answer is that you are the only one who knows. You have to gauge their level of responsibility—it's your call.
That said, most kids are ready for some supervised knife use at age 6 or 7, and they may have earned the privilege of having their own knife shortly thereafter. Between 8 and 9 years old is a great age, I think, because by that time they're really starting to develop good habits and are taking personal responsibility in other areas of their lives.
Remember, you don’t have to give them a Sebenza and send them out on their own. Take it a step at a time and don’t rush things. They won’t grow up tomorrow. You have a little time.
For more information, visit our Knives for Kids page.