After talking with one of our stud sophomore RB's who can throw around some big weights already but had some non-contact injury issues last year, I had to share something that I believe is critical in the development of all HS athletes. Also something I am working hard to correct and develop in all of our baseball players. Super important that athletes are working a combination of bilateral (squat/deadlift) and unilateral (single-leg squats, split squats, etc.) exercises. I have seen and continue to work with players that can squat or deadlift big weights but cannot resist two fingers of pressure when performing manual muscle test for glute medius strength.
Why is the glute medius so important in athletes? Because it is one of the primary muscles involved in stabilizing the hips. Simply put, your young athlete will move better and more efficiently, with active/strong hip stabilizers.
Long-story-short, if you are paying someone to train your child or they are using a HS training program, ask if they are doing any single-leg work? If not, then they are not receiving very good training. There are a lot of other pieces to the puzzle but this is something simple that all coaches who train athletes should be able to incorporate into a solid training program.