A number of studies are reviewed in an attempt to identify those schooling inputs that affect schooling outcomes, specifically cognitive achievement of students, in developing countries. Part 1 of the paper outlines the nature of the major tool of analysis, the educational production function (EPF), and the problems associated with its use as a policy tool. Part 2 examines how it can be used despite these problems and summarizes the findings of many studies on the U.S. educational system as a basis for comparison of findings from studies of poor countries. Part 3 critically examines nine studies completed for developing countries, and the conclusion synthesizes their findings. Two other studies using different statistical techniques are examined in the appendix. Inputs identified in all studies as having a positive impact on performance are employing highly motivated teachers, providing a minimum number of textbooks and access to general reading materials to all students, and promoting the use of homework as a teaching method. (Author/MLF)