Over‐ and Under‐achievement in Reading: Distribution in the General Population

S ummary . Empirical findings are presented on the distribution of over‐and under‐achievement in reading in five general population groups encompassing four age‐groups and two parts of the country—a major city and an area of small towns. It is shown that reading achievement does not exactly parallel IQ at all levels of intelligence, confirming the inappropriateness of the achievement ratio and like statistics. It is argued that over‐ and under‐achievement are best defined in terms of a regression equation based on IQ scores. Defined in this way, reading ability follows a generally normal distribution, over‐achievement and under‐achievement occurring with roughly the same frequency. However, there is a significant departure from normality at the extreme lower end of the curve such that gross under‐achievement in reading occurs at well above the expected frequency. This suggests that there is a meaningful group of children with specific reading retardation which is not explicable simply in terms of the bottom of a continuum.