I have watched som of these kids at the same weight for the past two years or better and don't understand how these kide don't grom My kids jump about 8-12lbs per year and about 3-5" height and these kids stay the same. If coaches are trying to keep the kids at one weight with normal groth sizes how can we have the same weight. If you grow and the weight stays the same then your muscle is not growing in proportion.
My oldest son has gained 6 lbs in 6 years. His coaches have him on 150 calorie a day diet. They also have me chain him up out back of the house between practices & weight lifting. It seems a little much but it keeps him competitive.