Each child may have several different things, including their environment, education, and so on.
So, maybe each child has their own ideal time.
It's just that I personally want to do it when I see my children are ready enough for the existing conditions. Whether it's at their age when they are in junior high school or senior high school. That might be around 15 years old, but only for some things that are still basic and seeing the conditions whether it is too forcing them or not, and seeing how they respond when I introduce this to them, to be able to continue or postpone it first.