It is much more important to understand the "why?" behind the depth limits for kids than to know what agency says what.
Like pregnancy, there are things about growing children and the possibility of decompression sickness we just don't know, and no one wants to find out! The main physiological concern with children is that we just don't know what any bubbling in the epiphyseal line might do to long bone development. Having a depth limit of 40' for youngsters is designed (in part) to limit the possibility of a DCS hit there and perhaps having a child with inhibited long bone growth - that is, ending up with one leg shorter than the other, etc.
Now there are plenty of youngsters who've gotten away with diving far deeper than agency recommendations - my own daughter is one, but when I caught up with her I made damn sure her ascent was super slow with a very long time goofing off in the shallows before surfacing.
So while there's no hard evidence to support keeping kids shallow, I for one have plenty of concern for keeping things super-conservative... and long bone growth is just one of the factors.
Rick
