A major problem in mainstreaming and implementation of Public Law 94-142 has been in establishing evaluation criteria to determine appropriate learning environment placement. Providing appropriate education in the least restrictive environment is primarily the classroom teacher's responsibility, requiring decision-making based on these questions: (1) What am I doing?, (2) Why am I doing it?, and (3) How do I know what I am doing is effective? To guide this decision-making, the 6-S paradigm was developed as a model for representing an instructional system, permitting teachers to reduce instructional systems complexities and develop programmatic solutions. The paradigm's components include (1) Someone--the classroom manager; (2) Something--the content of instruction; (3) Somebody--the student; (4) Somehow--the strategies and tactics for guiding learning; (5) Somewhere--the learning environment; and (6) Sometime--time-relevant factors including scheduling, pacing, and readiness. Using the paradigm as a framework, teachers can generate questions affecting program implementation and development decisions. A major problem in answering these questions is student and delivery-system variability. A teacher-directed rather than a teacher-related research model approach to answering 6-S questions is needed. (LMM)