This article reports on a two-part study of African American children's uses of various forms of the /-s/ suffix. Part 1 of the research consists of a careful replication of Torrey's (1972) experimental study to investigate the correlation between language and educational achievement. This replication study involved the administration of a series of pre- and posttest measures to determine surface-level uses of four /-s/ morphemes among 17 second-grade students. In addition to these assessment measures, a worksheet-based, explicit instructional program took place between the preand posttests in order to establish whether training could have the effect of bringing to a surface level the sibilant morphemes that might otherwise be hidden in the students' underlying grammar. Part 2 consisted of a replication of Torrey's study with a slight variation to her instructional component. This part of the study administered Torreýs pre- and posttest measures to a different group of 14 second-grade students, but provided a literature-based instructional program in which the students were taught the various /-s/ morphemes using multicultural and African American literature. Findings revealed that the explicit instructional approach was most useful when teaching some morphological concepts but a literature-based instructional approach was most useful when teaching others. These findings suggest the need to reflect diversity and flexibility in the design and implementation of assessment and instructional materials. The findings also suggest that decisions about teaching Mainstream American Academic English (MAAE) to speakers from diverse linguistic backgrounds should be based on students' overall patterns of linguistic competence rather than on observations of their language use in limited contexts. A number of implications for classroom practice are considered, including the need to develop links between studies in language and linguistic competence and the planning and implementation of learning programs.