As an instructor I think that you really have to consider the maturity levels here. I know few 10 or 12 yr olds I would consider taking deeper than 10 feet. Personally I like my students to be at least 16 "my preference" even then if they cannot display that they will be mature, responsible, and above all SAFE divers, I will not certify. And on the other hand I have found a few along the way that have been more mature than my older students..lol. So I guess it depends on the student wether or not they are ready.