My son is about to turn 10 and we were thinking about bringing him down to Florida to get certified. I'm sure I could find a place to do it but not sure if that is really the best approach. At my LDS they admit that 10 years some kids are ready to get an Jr OW certification but most are not according to them.
I taught my boys when they were around 8 or so. They were diving open water at 9. I remember allowing my 9 yr old to spearfish with me in 60 feet. I think back now and it seems way too young. But we never had any serious close calls and they received training that was much more intense and extensive than a child will receive in a normal scuba class. They were also trained from early on to use a redundant scuba system (pony bottle).
Most 10 yr olds are not ready for it, but some are. Some 10 yr olds can ride skate boards and dirt bikes and do gymnastics and all kinds of other very dangerous sports that require a high degree of coordination, concentration and the ability to perceive danger and consequences.
Scuba for young children requires a special aptitude for water. The problem is that most kids aren't "water babies".. My kids were snorkeling with me seeing shipwrecks in 90 feet (from the surface) when they were 4 yrs old.
I strongly encourage anyone who is even thinking about getting their child certified at that young age make sure that they are excellent swimmers, decent freedivers and can throw all their snorkeling gear into the dive well, jump off the side of the pool, swim down 12 feet, clear their ears, put on their fins, put on their mask and clear the mask and snorkel before hitting the surface (and do it with ease). If they think stuff like this is fun and easy and they really WANT to do it, then maybe scuba is cool for a 10 yr old. My boys wanted to learn very young, my daughter (who is also good in the water) has just started interest in it at 15 yrs old.
The other thing I think is a must is that the parent that will be diving with them needs to be extremely comfortable and experienced, because they will be diving solo.
I guess it is time to drag out the old (crappy) video of my 10 yr old wreck diving with me.. Kids CAN dive.
[video=youtube_share;w2NcsMdOWLA]http://youtu.be/w2NcsMdOWLA[/video]