No, exercise is good but the extremes athletes put their bodies through is not healthy; is bad for developing bodies, and the changes and consequences are often not even discussed for any kind of consent. In example i recall the story of a woman dealing with chronic pain because she wanted to be a dancer when she was 6 and her parents just signed her up with no discussion.

Also in contrast trans kids tend to be constantly warned of the effects and changes yet get discouraged, gate kept, gaslit, and abused more often than affirmed.

If they qualify, why not?

I'm sort of interested in this. The last time I looked at this issue I believe the consensus was that there is no pre-adolescent training effect, so just let kids run in an unstructured way for fun. When puberty hits, you get a training effect, but hard training should wait until the growth plate closes. I'd be interested if there were updated advice.

I wonder if we should ask the best runners in the world.

https://ourkenya.com/Sports/Why-Kenya-Runs

"Running culture begins in childhood. Kenyan children run to school, sometimes covering 10-15 kilometers daily by age eight. This is not training in the modern sense but transportation and play. These miles build aerobic capacity in a critical window of development, creating a deep physiological base that European or American distance runners, who typically begin systematic training in their teens, never develop. Barefoot running, which was standard in rural Kenya until the 1990s, develops foot strength and proprioception differently than shoe-dependent running. By the time a Kenyan runner reaches age 16 and begins formal athletics training, they have accumulated 100,000+ unplanned running miles."

So now that there is a story linked...the story misses the point. The issue is not acute injury, which is what the article discusses, but long-term injury by over training adolescents before they are ready.

Marathon training involves base training to bring up mileage to a minimum number (we can debate what that number is, but it's over 20 miles a week). Base training is followed by a 16-20 week cycle of increasing mileage and increasing the length of individual runs. Training will involve at least 3 runs over 3 hours in length. At a cadence of 180 foot strikes a minute each of those long runs produces 10,800 foot strikes an hour or somewhere from 30,000-40,000 foot strikes in a single session. And there will be 3 or 4 other sessions in a week.

Is that something developing bones should be exposed to? What are the long-term implications of exposing open growth plates, partially calcified bone, and immature connective tissues to high loads of repetitive stress?

Running has taken generally taken a conservative approach and limited mileage for younger participants. High schoolers focus on short distances, generally under 5000 m.

I think you're missing a link as there just looks to be an image and nothing else.