The influence of physical or mental defects also deserves recognition here as a possible factor relative to school failures, although this study has no data to offer of any statistical value in that regard. A few pupils in high school may actually reach the limits prescribed by their 'intelligence quotient'[15] or general mental ability, or perhaps, as Bronner[16] so interestingly points out, be handicapped by some special mental disability. If such be true, they will doubtless be found in the number of school drop-outs later referred to as failing in 50 per cent or more of their work; but we have no measurement of intelligence recorded for them to serve our purposes of prognostication. In the matter of physical defects alone, the report of Dr. L.P. Ayres[17] on a study of 3,304 pupils, ten to fourteen years old, in New York City, states that "In every case except in that of vision the children rated as 'dull' are found to be suffering from physical defects to a greater degree than 'normal' or 'bright' children." The defects of vision, which is the exception noted, may be even partly the result of the studious habits of the pupils. Bronner[16] remarks on the "relationships between mental and physical conditions," and also on how "the findings on tests were altogether different after the child had been built up physically." But Gulick and Ayres[18] conclude that it is evident from the facts at hand that if vision were omitted the percentage of defects would dwindle and become comparatively small among the upper grades. This would probably be still more true for the high school; but this whole field has not yet been completely and thoroughly investigated. It would be very desirable to have ascertained the size of the classes in which the failures were most frequent, as well as the relative success of the pupils repeating subjects in larger or in smaller classes. But, as such facts were unobtainable, it is permitted here simply to recognize the possible influence of this factor. It seems deserving in itself of careful and special study. From the standpoint of the pupil, the kind of subject, the kind of teacher, and the sort of discipline employed will tend to influence the size of class to be called normal, and to make it a sort of variable. Thirty pupils is regarded by the North Central Association as the maximum size of class in high school.[19] Surely the size of class will react on the pupil by affecting the teacher's spirit and energy. Reference is made by Hall-Quest[20] to an experiment, whose author is not named, in which 829 pupils stated that their "most helpful teachers were pleasant, cheerful, optimistic, enthusiastic, and young." If such be true then the very large size of classes will tend to reduce the teacher's helpfulness. 2. THE EMPLOYMENT OF THE SCHOOL ENTERING AGE FOR PROGNOSIS