Randy,
I am going to have to check that Bronze book because I thought it actually said 10 to 12 years old depending on the kid.
This is a controversial topic but I believe that many responsible professional people both trainers and medical people are starting to advocate certain types of strength training with weights both to assist in preventing injuries and in improving strength for young kids. It is not for everyone and every kid is different as far as when they are physically and mentally ready to start a program. Some maybe would not be ready until they are in high school.
I actually started my son on a program when he turned 10. I tried doing the exercise program that Randy suggested with the pushups,etc. but my son did not like it. He loved doing the weight workout and has been doing it for three years. I researched it by buying a book on strength training for young athletes and consulting with a friend of mine who is a high school strength training coach.
Some of the keys I learned were that first you need to emphasize safety in your workout room and teach that to the child. Don't leave weights lying around and you do not play or run around in the workout area. That is important for siblings and spouses to know too. Second you do the exercises with proper form. If you do not have weightlifting experience, you should get them involved with an experienced coach. Third do not get them into the syndrome where they want to see how much they can bench press one time. My high school friend set me up on a program where on his heaviest lifting day we do not use any weight that he cannot do at least eight times in a repetition. From my research the way to avoid injury is to have them do lighter weights with more repetitions in contrast to a program where you just try to lift the maximum amount one or two times. One day my son does repetitions of eight-the heaviest weight day, one day he will do repetitions of 10 with slightly lighter weights and one day he will do a very light day with repetitions of 12. You always should have at least one rest day in between strength training sessions.
If anyone is interested in starting a program for their child, my advice is to research it and to go very slow at the start.