I can't give any specific recommendations, because I've never had to train a young person. However, I can confidently say I know what I would start with and that is training of connective tissues. I very much wish I could start all over, because I would concentrate on training this part of my body, which is why so many athletes, both professional and amateur are sidelined.
Every time I've had an injury or known of someone that injured themselves it almost always involved connective tissue. When I hiked the Appalachian Trail, it was the downhills that sent most people home with knee/ankle/hip injuries. Contrary to popular belief, it's NOT the uphills that are the hardest in hiking thru the mountains. They are tougher on a cardio level, but the downhills destroy connective tissues -- cardio is incredibly easy to build in comparison.
The problem is, with our strength training, which focuses so much on muscle strength, but ignores connective tissues.
This lady talks about that fact in the video, especially at the 3:40-minute point in the video. These traditional strength exercises are good, I'm not bashing them and I still do them; however, when we ignore the health of our connective tissues, we're setting ourselves up for injury.
There are a lot of good videos on YouTube, but one of the really good ones is from this guy who suffered much of his life with joint pain.
https://www.youtube.com/@TheKneesovertoesguy