In recognition of the need for understanding, and for making proper allowances for differences in body growth and physical development during school life, it has been the custom at the Manchester Grammar School to take annual measurements of standing and sitting height, girth of chest, of upper and lower arm, and also range of vital capacity of all the boys amounting to about 1000 in number, and to compare their physical growth with their school attainments. The measurements are graded for each boy as regards height, weight, chest girth and vital capacity, in order to discover the rate and range of growth in each category, and see how far the growth in one category is commensurate with the growth in another. The grading in each category is expressed in time-increments of six months' growth above or below the normal boy of his age, so that, e.g. a boy who is a year ahead or a year behind the average boy of his age in height is graded + 2 or − 2 in height, and so forth. Similar and separate gradings are used for weight, chest girth and vital capacity. At the time of annual measurement, enquiry is also made into the physical activities in which each boy participates, e.g. the games he plays, his performance in the swimming bath, in the gymnasium, etc.