Calculation of sex- and age-standardized growth metrics based on the 2000 CDC growth charts for children and adolescents with ages of >= 24.0 to < 240 months. Provides functions to generate z-scores and percentiles for weight, height, and body mass index (BMI) using the LMS method (lambda-mu-sigma). Includes extended BMI z-scores for values above the 95th percentile to more accurately characterize the sex- and age-standardized BMI of children with very high BMIs.