1 reason kids like splits is that they are chasing the soreness. Almost all of us fell into the trap of thinking that big soreness=big results. If you do full body routines, you can do the same volume on each muscle group, with much less soreness.
We understand that this is a GOOD thing, but it's the opposite for people who think that soreness is good, and the more the better.
In the end, it's up to the coaches who work with the youth to educate them correctly from the get-go, but this seems to be a rare thing. My coaches didn't know anything about form or programming. By the time I left high school I knew more than most of my coaches, and I didn't know squat.