Adult chess improvers are different from children in many ways and have different strength and weaknesses. Also, their life situation is very different (e.g. much time and little money vs. little time and much money).
However, this rarely seems to be considered by courses, chess improvement plans, books, and other materials. The readers are given a 'one size fits all' solution/advice. It works, but it could certainly be better or more efficient, if the situation and different strengths and weaknesses of the learner would be factored in.
Are there any resources with explicit guidance how to adapt training for children or adults, taking into account their strengths and weaknesses?
For example, teaching a strong child the Najdorf as their new main opening may be reasonable. It'll absorb the variations much more easily into its memory and get an intuitive 'feeling' for the Sicilian positions. However, it is more difficult for adults to learn new things and memorizing and understanding concrete Najdorf move orders would take a lot of effort. Not to mention being able to understand and handle the resulting positions well. In this case, their little time would be much better spent on practicing other skills, learning a simpler opening instead with easy to remember moves, common structures and plans, even if it is an opening that a child would call 'boring'.
In my impression, adult improvers are more willing to learn something even if it is temporarily not exciting to work with, they tend to think more logically and abstractly. However, their brains are not that plastic anymore, and they probably will not develop the same level of pattern recognition, visualization and intuition. Children pick up concepts more easily and 'on the go'. Their knowledge will be more implicit, whereas one needs to explain an adullt improver what a 'bad bishop' is in explicit terms. Children want to play 'fun' chess, wild attacks, sacrifices, traps, while adults are often very materialistic and cautious.
