This paper reviews and summarizes research studies in writing and related language areas that help educators to understand how writing is socially based. The purpose of the paper is to cast classroom practice in the variously dim and gleaming lights of research and theory, linking practice, research, and theory by looking with a close-up lens at the ways in which writing and other language experiences inside and outside of school have been studied and explained. Using this lens, the paper first presents some theoretical perspectives on written language acquisition and development. Next, the paper reviews studies that investigate social contexts for writing development both in school and out. The paper then looks at studies of instructional practices in writing that are, from lesser to greater degrees, socially based. The paper concludes with a presentation of some "core concepts" which capture the ways in which some of the most promising instructional practices in writing are linked to social theories. Ten notes are included; 213 references are attached. (Author/RS)