MUCHterest has been taken lately in the changing growth rates in school children. Daley1 gave a detailed report on heights and weights recently obtained from various London districts, and Spies and his co-workers2 published an account on the determination of status and progress in children with nutritive failure. Spies and his associates based part of their findings on Wetzel's grid, which is similar to that described by one of us3 elsewhere. Trends of growth may, of course, be estimated by calculating the means of height and weight at each age, or weights for each height, irrespective of age, but many more children than are generally to be found in one school would be needed in order to arrive at a definite estimate. In the following a method is described by which the medical officer, without much labor and arithmetic, may easily test the trend in single schools