I have worked with a lot of kids over the past year. Under the supervision of a scuba instructor, I taught some kids snorkelling. One turned 12 this year & was given scuba lessons as a gift from his diving dad. He has better skills as a result of snorkelling & skin-diving than some kids his age have going in cold. I think that snorkelling is a much more age-appropriate activity for a child.
I have (as mentioned in another thread) assisted in SASY programs (Supplied air snorkelling for youth.) This program can be appropriate for kids under 10 or in their teens. The success rate as others have mentioned can vary by the kid. It can also vary by the amount of time the program lasts, the resources available to the program, & the time of year the program occurs.
Kids have pressures in life that we adults don't relate to: homework in school during the schoolyear that preculdes study of the scuba writtten material, childlike boy-girl relations that make many kids unable to be effective buddies in class, shyness with strange adults that make them fear asking questions or attracting attention till there is an emergency, inappropriate competition issues in the water, transportation issues as they rely on adults with other obligations to drive (and parents often don't take the child's obligations seriously, althought the primary relationship seems to be between the parent & the instructor, not the child & the instructor.) I have had some wealthy spoiled kids treat me as a servant, expecting me to shlep their gear. Their parents could stand to teach them to be kind to servants.
So your kid is "different" and smart & special. Some are. I have seen many kids who were raised in the ocean & can do a rescue at age 10. But I notice that this discussion is among adults, the ones who have to teach or pay for this hobby for the kids. Obviously, a child cannot decide independently to spend thousands of dollars on classes, equipment & travel, so he MUST have parental approval (if not pressure) to do this. I really wonder with many of these kids who the classes are for, anyway.
I suspect in some cases that there are some family dynamics other than a child's interests at work, ie: a divorced parent trying to find a way to monopolize a child's time in a scenario that the other parent can't participate in. Or, perhaps, Mom or Dad is impatient at the idea of having to snorkel with the kid instead of doing what (s)he really wants to do (her)himself. I have only met a couple kids (in a subsidized SASY program) who wanted to do this to be among friends their own age. SCUBA can be a great part of family intergenerational recreation (as part of a camping trip, etc.) and a few kids see it as a way to feel more grown-up like mom or dad. Because kids have to dive with parents, however, diving can contradict the need many kids this age have to hang out with their pals. One 12-year old asked me after a dive, "Are the grown-ups really happy after a dive, or are they all just drunk?" Guess. Fortunately, he had his Walkman.
Most kids under 13 who I see in scuba do not finish the program. Like tuba lessons & modern dance, it was fun until it became work. The books are written to be accesible, but the vocabulary and density can be a little over the heads of a child. Is the adult prepared to assist in homework of another subject? One 11-year old girl sat in the classroom sessions mugging for her dad, doodling, and antzing around. Sitting still for several hours was too much for her.
From a leadership point of view, the responsibility heaped onto the instructor is way more than the class fee can cover. Not only is the instructor given the added pressure of keeping someone's kid safe, but he must also entertain & engage someone with a naturally short attention span. Would the child himself really be considered responsible if he were hurt due to not paying attention? I honestly have surmised that this marketting push realizes full well that this lowering of the age bar simply harvests the funds of parents with lots of cash.
There are always kids who can drive, fight a war, vote responsibly, and pass medical school at age 10. They are exceptions, but they exist. Perhaps they should not be held back because there are others who will not think as adults till they are 40. It is the parents & instructors who move these little pawns around. Neither party has much information yet about the dynamics of working with this age group in SCUBA. My suggestion for thos who think their kids want to persue the sport is to see how they do in a skin-diving program with kids their own age for a while. Better to spend $150 on basic gear than thousands on scuba stuff for a kid who finds that he really does not want this as bad as others want it for him.