I really feel for your son. I was very very bad at PE. I remember really wishing for rain or snow so that PE would be cancelled. I am not good at anything sports related. Luckily I grew up in China where being good at academics was way more important than being good at sports. Plus I was a girl as I believe it is much harder for boys to be so bad at sports. As an adult I often wondered whether I had a disability of sorts. I never pursued a formal diagnosis but I do have a lot of joints and ligament and muscle pain now in my forties. I have no idea whether any of these are related though. But it is also likely that I simply was in the bottom 5% of abilities or whatever the low end of normal for physical abilities may be.
Also our PE was mostly testing about speed and skills and left me with nothing I can fall back on as a preferred physical activity.

I won't lie that it was really hard for me to be the last in everything in PE every year. But I have also always said that it was the one thing that grounded me so that I won't be too prideful. I wish our PE was less about testing and competition and more about teaching me a skill that I wasn't so turned off by it.

It was really hard I won't lie. I think the most important thing is to make him proud of other things that he is good at, which I am sure are many. Just know that as an adult, it has not really impact me much. Although I do wish I can run so that I can go out jogging with colleagues at conference or just keep up with my son.