I know everyone hates these posts about kids....
My son just turned 11 and today ran 18:39 for 5k. Wasn't downhill and course is certified. He is on the small side and hasn't hit puberty.
How does this rate? A year ago he ran a 5k in around 21:30 which was about what I expected. I was surprised to see him go this fast.
Don't worry I don't think he is going to be the next great thing, was just shocked he took so much time off.
He is a swimmer and runs for fun.