It should now be recognized that every child has at least five parallel ages: A "chronological" age, in years, months, and days: a "physiological" age, indicative of physical growth and maturity; a "mental" age, significant of intellectual capacity and ability; a "school standing," or "pedagogical" age, denotative of relative position in school grades and a "moral" or "religious" age. These ages may or may not coincide in their stages of development. In a first-class school the school standing, or pedagogical, age and the mental age would be the same. This monograph aims to present the results of a study of the physical growth, or "physiological" age, and the "school standing" of a group of boys and girls from 6 to 18 years of age when observed consecutively. The scope or field of the investigation includes: (1) A series of norms based on the height and age distribution, and weight and age distribution; the averages and average variations of individual increments of growth in height, weight, and lung capacity; and the individual growth curves in height, weight, and lung capacity, with health notes and weight-height and vital indexes; (2) An investigation on school standing in marks, grades, and ages; (3) The relation of physical development in height, weight, and lung capacity to school standing; and (4) A brief historical summary of the work in this field, with an annotated bibliography. The chief value of the monograph consists in the fact that it is the first attempt to follow consecutively the same groups of children through the elementary and high schools, either in physical growth or school standing, or the relation of the two. Since the curves and records represent individual histories, they will be of permanent value. The monograph also aims to give the present status of the problem of physical growth. A bibliography and an index are included. Individual sections contain footnotes. (Contains 40 figures and 34 tables.) [Best copy available has been provided.]