Elements of effective planning in special education are considered, and a Hawaii project, Model T, is described. The project focuses on the process of making and evaluating resource decisions, such as decisions about the kind and frequency of related services staff time versus instructors' time. Microeconomic concepts such as diminishing returns and input substitution are used in decision making, particularly for severely/multiply impaired students requiring greater staff time and more related services. Early findings of the Model T project suggest that allowing individuals other than specialists, (i.e., parents, teachers, and aides), to carry out some planned related services activities without removing the student from the classroom will be more efficient and effective. A formula is described which depicts the possible resource combinations or substitutions to meet related service needs. (CL)