This article reports the data on sex differences in school achievement yielded by the Iowa Every-Pupil Testing Program, high school, for the years 1932 to 1939, and the Iowa Every-Pupil Basic Skills Testing Program (Grades III-VIII) for the year 1940. A brief review of representative articles dealing with previously published investigations of a similar character is also given.A REVIEW OF THE LITERATURE This brief review chiefly treats sex differences in achievement test scores, although attention is called at the outset to sex differences in school marks, promotion, acceleration, retardation, and similar evidences of school progress. In his Laggards in Our Schools, 1909, Ayres 2 concluded that "our schools as they now exist are better fitted to the needs and natures of the girl than of the boy pupils." He based this conclusion upon an analysis of the records of several hundred thousand pupils in various cities of the nation. In 7624 high schools in 1906-1907 there were 314,084 boys enrolled in comparison with 419,570 girls. In the elementary schools in fifteen cities, having an enrollment of 282,179 pupils, he found retardation among 37.1 per cent of the boys and 32.8 per cent of the girls. Approximately 23 per cent of the boys were repeating grades in comparison with 20.2 per cent of the girls. It is known that in recent years the number of boys in high school more nearly equals the number of girls.St. John's 16 data on retardation and acceleration make possible sex comparisons at comparable IQ levels. His investigation deals with the progress, over a four-year period, of about five hundred boys and four hundred fifty girls, Grades I to VI, chiefly I to IV, enrolled in the schools in a residential suburb of Boston. Table I shows the sex comparisons. St. John's data also show that correlations between IQ and achievement data were higher for girls than for boys. In marks of conduct and effort girls achieved a greater degree of superiority than in any of the other measures used.Johnson's 9 analysis of the records of the high-school pupils in St. Louis is to the same purpose. His data are shown, in part, in Table II.