So another issue I see - both with this topic in general and in this thread in particular - is a lack of consensus over what "good coaching" means.
Taking pre-pubescent children and loading them up with acidosis tolerance work is greedy, ineffective, and tends to be detrimental to the child long term, both physically and psychologically.
1)The ability to develop this capacity is lesser pre-puberty than it is post-puberty. Bang for the buck is poor.
2)The opportunity cost of choosing this work over aerobic development and max velocity development means that the pillars these children could be building stronger are being neglected for short-term gain. Meanwhile, little soccer and basketball girls are building these capacities, increasing their general athleticism and thereby reducing their future injury risk.
3)Extracting every bit out of a child when she is young and getting her to that next level, whether it be JO regions, nationals, whatever, tends to run hand-in-hand with children cementing their identity as a stud runner early. Not all, but many, of these child phenoms struggle with the psycholigical toll of everyone else "catching up" to them as they get into the meat of their high school years. With females, this toll can amplified if the journey through puberty temporarily slows them down and the next tiny girl comes in and becomes the next big thing.
IMO "good coaching" of talented 7th graders would feature a lot of three things - aerobic development through a frequency of not-balls-to-the-walls continuous runs, max velocity and general athleticism development through a diverse array of sport and game, and a focus on FUN. I would NOT be cranking the 400's on the track much if at all, and I would race the kid sparingly. Sadly, the need to put one's ego aside and defer the "reward" of elite performance for another coach further down the pipeline is too much for many.