My father was a member of a local club, which I joined at the age of 12, in 1967.
I spent the first 2 years going through the same snorkel training as the adults, this was the old BSAC A,B,C,&D tests, these included swimming 2 lengths of the pool with a 10lb weightbelt, holding my breath for 30 seconds, lifesaving (which came in useful later in life) Also duck diving down 20 feet in a lake to retrieve objects from the bottom.
At 14 I was allowed to progress onto aqualung training, this was again the same training as the adults, no concessions for being young.
At the age of 16 I discovered motorcycles & girls this put a stop to all diving, until 1993 when I re-joined the same club, and went through all the training again.
The point is at that young age I knew nothing of the dangers of diving (DCS, gas toxicity etc)
I had my father to look after all that side of things, when he said time to go up I went up, life was so simple then.
Now I’m a father my self with a son who started diving at the age of 14, my club has a policy that no one under the age of 16, can join our club unless they have a parent who is a diving member, to take full responsibility of their child, also no one under the age of 14 may use an aqualung.
I feel anyone under that age is not strong enough to be able to handle the equipment & the training.
Diving at a young age has done us no harm, there are far more dangerous things out there in the world, the biggest damage done to myself & and my son was done by motorcycles & bicycles.