Ever since I learned about PE from this wonderful website I have been asking myself how much bigger I could have been by that age if I had started PEing when I hit puberty.
I may be getting slightly off topic, but I think it would be a reasonable hypothesis that if you start PEing WHILE you are developing and growing, you could grow much more than if you simply try to stretch out the tissues that have stopped essentially growing (as most of us are doing).
If I have a son I think I will teach him about PE at ~ 13 years of age, give him a good head start (if he is so inclined).
I used to think “wow if my dad only gave me a hint when I was around 12”, but actually I know it would freak me out badly. To realize that you “Would be THAT big if you only started THIS age” one need to grow older, meet girls. Even If my dad knew about all this somehow, I’d rather have him not telling me until I was like 18. Seriously, you have the whole life to PE. Don’t try to rush it so you get a fine 8x6 as your 18 birthday present. I know it’s tempting, but If your son won’t like the whole idea or won’t understand it right away, you may creep him out.
I’d only suggest only giving a hint about Kegels since it’s health related more than PE. From there he’ll find the way to PE soon enough.