Two studies were conducted to examine the efficacy of direct measurement, standardized achievement tests, and aptitude-achievement discrepancy scores in distinguishing learning disabled (LD) and nonlearning disabled (NLD) students in grades 3 to 6. For both reading (Study I) and written expression (Study II), students' scores on direct and repeated measures (Words in Isolation and Oral Reading) predicted their classification as LD or NLD as well as commercial measures of achievement (Stanford Diagnostic Reading Test, the Peabody Individual Achievement Test, and the Test of Written Language) and aptitude-achievement discrepancy (the Woodcock-Johnson Psycho-Educational Battery). However, the direct measures required significantly smaller expenditures, both in terms of cost and time. The additional benefit was the use of direct, repeated measures to obtain common data bases across decisions affording continuity between information collected during assessment and the information needed to evaluate instruction. (Author/PN)