Three concurrent validity studies were conducted to determine the relationship between performances on formative measures of reading and standardized achievement measures of reading. Correlational analyses for five formative measures and three standardized measures provided evidence for the validity of Words in Isolation, Words in Context, and Oral Reading as indices of reading achievement. Comparisons of performance of regular and resource program students in grades 1 through 6 revealed marked differences between the two groups and across grades. The usefulness of the formative measures for continuous evaluation of student growth in reading is discussed. (Author/CL)