Here's what you should know before you sign them up.
The stalling, the refusals, the fear, the anxiety and the intimidation: It's all normal.
My 12-year-old daughter hates exercise. I mean, she really hates it. With a passion I would love to see in her studies or efforts to keep her room tidy.
If you haven't heard the name Sabre Norris, get ready to start hearing it - a lot.
"Losing builds character" is a hard expression to swallow when your nine-year-old athlete climbs into the car sobbing after yet another defeat.
Gabi Shull, from Missouri, America, was diagnosed with Osteosarcoma in her knee after an ice skating accident when she was nine years old.
"In my dreams I wouldn't dream about of anything like that. Because I think it was an accident. It was just as amazed as I was."
Alistair and Jonny Brownlee were brothers in arms at a dramatic finale of the World Triathlon Series as double Olympic champion Alistair hauled an exhausted Jonny over the line.
Meaalofa Te'o, 9, looks unstoppable on the football field.
"Having ADHD and taking medicine for it is nothing to be ashamed of, nothing that I'm afraid to let people know."
"When it comes to the pursuit of extra-curricular activities, parental anxieties run deep," writes Kasey Edwards.