The interaction between theoretical linguistics and language teaching has historically been problematic. This interaction is viewed here from the standpoint of educational linguistics, which is the intersection of linguistics and related language sciences with formal and informal education. The issue is the relevant educational problem that knowledge about language acquisition could help solve. To this end, three related questions from the fields of psycholinguistics and language acquisition are investigated: (1) What is the normal course of the development of language in an individual? (2) Given the normal range of individual variability in the development of communicative competence, what factors account for this variation? (3) Which of these factors are susceptible to control by an educational system? It is felt that the answers to these questions are basic to language education, since they both set its limits and suggest the kind of intervention that might permit helping each individual. (CLK)