Methods of selection of physical defects among school children have a far-reaching influence on the school health service as a whole. They must be practical and economical, of course, but that is only one way in which they affect the total efficiency. They also have an important bearing on the way the child is viewed by the school medical examiner to whom he is referred and on the type of information that the school nurse takes with her on the follow-up visit. How many of the children who are 7 per cent underweight for height are truly malnourished and how many of those examined are missed by this method? This query involves two sources of inefficiency—selection in error and failure to detect.
Such error of selection has a profound influence on the obligation of the school medical examiner to explain the case and prescribe further study. If the child is