Im 16 and a person who stutters, I was never to concerned about it when I was in elementary school. Until one day I had a really bad stutter in front of 80 kids at my school and got made fun of for a few days after that. Ever since then I have been way more self conscious of my stutter and it has gotten a lot worse. It inevitable that he will be insecure about it when he is a teenager no matter what his experiences are. I think it’s important not to tell him it’s something he should be insecure about. I grew up with everyone around me telling me how I should feel about my stutter when it’s something that they have never experienced in their lives. At the end of the day he is the one with the stutter and he knows what he is comfortable with.