this may or may not help but, i was 12 in 1977 when i first certed under NASDS. at that time there was little to no safety equipment and tanks were as big as me. the logic being at the time I guess that I could do the swim stuff and I had a grasp of the "science" behind it. A horse collar and hard pack, ahh the good ole' days... But I digress...
I guess my point is, if it was allright then, what has changed? Other than better gear, a better understanding of the dynamics involved, and more people willing to mentor or train, if the youth is up to it, then why not?