I have taught a number of children. As can be expected, they vary as to maturity level and ability to understand the material. However, most have been adequate as divers and at that age must dive with an experienced diver and with depth restrictions. (I think the agencies may have slightly different rules, I am PADI) I have found that teaching children is one of the most rewarding groups to teach. Their enthusiasm and the joy they experience when diving is very rewarding. I can still hear the kids squealing through their regulators when they see the fish, etc. I also recommend you find an instructor that has taught kids and enjoys teaching kids. It can take more patience than normal. Then you have to trust the instructor and let he/she be in control.