He has to learn the difference between earned authority and unearned authority.

Those who have experience in the subject are often giving him advice to improve his skills. Just as he can see what others are doing and see a better way, he is also observed and then provided with a better way to do things.

Tell him to try it as an experiment to see if its better. As he gets older, he may have to try several different approaches before he can decide which will work best.