Despite substantial research on children's literacy performance outside school, relatively few studies have examined the classroom context of writing development, and even fewer have considered the relationship between general classroom discourse and writing. This paper presents an ecological framework for studying the relation between classroom discourse and writing. The framework emphasizes the reciprocal roles of teachers and students and focuses on the types of questions teachers and students ask as indicators of classroom discourse. The framework is assessed with data on discourse and writing in 54 ninth-grade English classes and 48 ninth-grade social studies classes. In both subjects, it is found that classroom discourse and writing activities tend to proceed independently of one another. Regression analyses show that student writing benefits from classroom talk, especially when teachers ask "authentic questions" (questions for which teachers are not looking for particular answers) and incorporate student responses into the questions they pose (known as "uptake"). Student writing is also enhanced by instructional coherence among reading, writing, and classroom talk. Students who are required to write more frequently exhibit better writing in English class but worse performance on writing in social studies, a finding that may be explained by the different purposes of writing in the two subjects. Social studies teachers used writing mainly as a check on reading, whereas English teachers paid more attention to the writing process. Contains 4 tables of data, 9 endnotes, an attached analysis of a social studies test with 4 tables, and 42 references. (Author/NKA)