Using data consisting of descriptive and expressive-narrative essays written in 1969 and 1979 by black 17-year-old students in the stratified probability sample from the National Assessment of Educational Progress (NAEP), a study investigated which language patterns differentiated the NAEP essays written by black students in 1969 from those written in 1979. Narrative essays were scored using the primary trait technique while the descriptive essays were scored by using the holistic scoring technique. The total number of T-units and the total number of words were also tabulated for each essay. The distribution of black English forms was arrived at by the standard sociolinguistic procedure of calculating the ratio of actual to potential occurrences of black English. The data suggest that the performance by black students in narrative writing from 1969 to 1979 was influenced by a combination of the following factors: (1) a decrease in the use of black English features, (2) a decrease in the number of words, (3) the use of a scoring criteria based upon explicit features relative to the type of discourse, and (4) the assignment of a topic conducive to field dependent cognitive skills. Because these variables had an opposite effect upon the descriptive essays, writing performance did not improve. (HOD)