Thanks for the enlightening comment, Prof.
Actually, I said that training to failure can contribute to the semi-myth that weights can stunt children's growth.
I say semi-myth because if done improperly (excessive loads, poor technique, the usual jazz), children's partially formed growth plates can be put at risk. As back-up, I offer a section of article I had found, taken from the American Academy of Pediatrics official policy statement:
So, I still recommend avoiding muscular failure for kids (and most adults, but that's a separate issue), while advocating properly supervised, well rounded, weight training. Thanks.