Navin Johnson - Some of these people posting obviously dont have kids so ignore them. Their opinions don't count.
You dont have to be that "AHOLE" dad to make your kid better at anything. You can find creative ways to help improve your kid in any part of life.
I love how the 3 clueless posters above said "let your kid grow up and let him be a kid, no pressure". Wtf does that mean?
Lets apply that to school and see how great that philosophy turns out. "Well my kid keeps failing his classes and bringing home Fs but he is a kid, i am going to just let him grow up and be a kid". Yeah that makes no sense what so ever.
Physical wellness/fitness may not be as important as school and learning but it is still an important factor in life. If you are concerned about your kid then do something about it. It is hard to get kids at that age to take interest in physical fitness so you have to think of creative ways to keep them at it.
I would suggest starting a "Family fun, test or day" maybe a few days a week. Where you and your son both do the exact same things. At that age he should idolize you and want to do what you are doing. So lead by example. Run some quick sprints or squats/pushups in the morning. have him compete against times or reps or against you. You will know what his limits are but by keeping it fun you can push him to be better and later he will thank you for it.
You arent going to make him the fastest kid in school overnight but what you can do is instill good physical fitness values in him and with the small changes listed above, he will be light years ahead of other kids when or IF he wants to play sports in school.