The argument is put forth in this paper that the academic achievement of black children relative to whites deteriorates over time in school. The argument is substantiated by analyses of data from a statewide study of the standings of black and white children entering kindergarten and from two large National Health Examination Surveys of, respectively, 6- through 11-year-olds and 12- through 17-year-olds. To make comparisons among different ages and with data from more than one study, the "single standard" concept, a statistical technique used frequently by epidemiologists, was employed. In each of the age groups, the average score of the total group of subjects was established as the single standard. Meeting the average was taken to be the standard for subgroup performance; the actual average score of any subgroup was divided by the total group average. The resulting value may be regarded as the ratio of that subgroup's performance to the standard for the total population examined. Scores for different groups on the two parts of the Scholastic Achievement Test provide an example of higher ratios for white and lower ratios for black children. Results of applying the procedure to the state and national data are reported, and implications are discussed. (RH)