Boys and girls do their best work only when they concentrate their attention upon the work to be done. One of the greatest fallacies that has ever crept into our educational thought is that which suggests that there is great value in having people work in fields in which they are not interested, and in which they do not freely give their attention. Any one who is familiar with children, or with grown-ups, must know that it is only when interest is at a maximum that the effort put forth approaches the limit of capacity set by the individual's ability. Boys concentrate their attention upon baseball or upon fishing to a degree which demands of them a maximum of effort. A boy may spend hours at a time seeking to perfect himself in pitching, batting, or fielding. He may be uncomfortable a large part of the time, he may suffer considerable pain, and yet continue in his practice by virtue of his great enthusiasm for perfecting himself in the game. Interest of a not dissimilar sort leads a man who desires position, or power, or wealth, to concentrate his attention upon the particular field of his endeavor to the exclusion of almost everything else. Indeed, men almost literally kill themselves in the effort which they make to achieve these social distinctions or rewards. We may not hope always to secure so high a degree of concentration of attention or of effort, but it is only as we approach a situation in which children are interested, and in which they freely give their attention to the subject in hand, that we can claim to be most successful in our teaching.