Since the measurement of school achievement involves the administration of achievement tests to various grades on various subjects, both grade level and subject matter contribute to within-school achievement variations. To determine whether achievement test scores vary most among different fields within a grade level, or within fields among different grades, achievement test scores from 88 Israeli elementary schools were examined. Test scores of the resulting 15 combinations of grades by subjects were averaged. The average within-school variance was 25% of the total across-schools variance, showing notable heterogeneity. Computation of the within-school range for the 15 means showed 55% to exceed one standard deviation. Further analyses showed more similarity in mean achievements of the same grade level in different fields than of different grade levels in the same field. The first analysis, involving a within-school anlaysis, had three components: between grades, between subject areas, and the interaction. The second, nonmetric analysis of the correlation matrix between the 15 school means was conducted using smallest space analysis and ADDTREE. Furthermore, in 88% of the schools where over 51% of the within-school variance was caused by a single component, that component was grade level. (MGD)