I would think other kids would tease a kid who looked ripped like that....or maybe they wouldn't....I have always been told weight lifting at too young an age could stunt muscle development later. Also, some people just don't have the genes for getting "ripped" and can weight lift incessantly without those results. That's why many people turn to steroids out of desperation. I wouldn't want my kid feeling he had to be ripped, it's a self-image issue no different than other self-image issues like anorexia. Just my 2-cents. :)

Work with body weight alone. NO EXTRA WEIGHTS. The muscle tissue will respond slightly but the joints, bones and ligaments are not ready for it.

Those little growth plates will not be happy with too much abuse, what Markus said.