About 30,000 students in Grades 1 through 12 in Jackson, Mississippi, were studied to determine the effectiveness of instruction for all major social groups represented by the student population during the 1986-87 school year. The California Achievement Test and course grades were used to obtain core data. Demographic data were obtained for students. Focus was on illustrating the development of the district's evaluation processes and refining the district's process for identifying at-risk students. Multiple-variable and interaction analysis models were used to analyze the data. Results indicate that: (1) the models used are simple but powerful tools for evaluating school effectiveness; (2) considerable progress has been made by the district in the delivery of services to students from both upper and lower social classes; (3) a discrepancy remains in minimum mastery across some groups of students; (4) identification of at-risk students has been made more efficient; and (5) the education of poor children is politically and economically complex. Twelve tables and nine charts/graphs are appended. (TJH)