The conceptual focus of this study centers on a key aspect of improved schooling: the development of sophisticated thinkers in the K-12 sequence of education. The document is organized into four major sections. The first section describes how the theoretical bases of a thinking skills program are developed and rooted in the literature. In section two, the proposed program design is presented through the development of a 3-level model of thinking. Section three addresses implementation concerns such as instruction, staff development, subject matter integration, and program assessment. Section four presents a selected resource guide to indicate the kinds of materials and information that ought to be made available to educators to help them plan and create a program based on the proposed design. A concluding section summarizes the study and suggests how the overall design can be used by practitioners seeking to build a K-12 program. Seven appendixes provide a glossary of thinking skills; a checklist for materials considered in thinking skills programs; a thinking skills lesson plan; a general teaching algorithm; a student evaluation form; an appraisal of thinking skills throughout the K-12 curriculum; and a model of thinking skills: a basic processes continuum pre K-12. (Contains approximately 135 references.) (LL)