To provide classroom teachers with an understanding of some of the properties of language and of their effects on classroom interaction, this booklet reviews research in the area and offers teaching suggestions based upon that research. The first section of the booklet presents an overview of the American idea of language "correctness" and its origins and discusses the problems of trying to define "good usage." The second section examines how teachers influence children's learning of language through their own usage, their leadership patterns, their feedback, and their expectations. The third section deals with language acquisition, examining in turn the phonology, syntax, semantics, and social usage of language. The fourth section examines some of the teacher attitudes that foster students' linguistic development and outlines several activities that can be used to enhance language acquisition. The final section discusses ways that teachers can help older students develop skilled use of language and reviews the debate over nonstandard speech. (FL)