This paper describes the use of a writing strategy, Cognitive Strategy Instruction in Writing (CSIW), to improve expository writing and student responsibility of four seventh-graders with learning disabilities. CSIW emphasizes the need for students to take responsibility for their own writing performance and to scaffold one another's writing development. The year-long study incorporated collaborative writing by the students within a special education resource room setting. Theoretical discussion examines social constructivism and the roles of student and teacher in constructivist dialogue. Principles of the CSIW model are explained, including: effective writing is a holistic enterprise; immature writers benefit from writing apprenticeships in which the teacher models the thinking of effective underwriting; and students collaborate to write for authentic purposes and real audiences. Also explained are the CSIW instructional program and the taping of all instructional sequences and writing-related student conversations during the year for later analysis. Pretest and posttest analysis revealed impressive growth in the students' writing skills on the taught and practiced essay structure though not for an untaught and unpracticed expository structure. Many examples of classroom dialogue illustrate teacher modeling, teacher scaffolding, and classroom conversation showing peer support and the transfer of responsibility to the students. Appended are sample CSIW "think sheets." (Contains 39 references.) (DB)