This report describes various components of the process of disaggregating student achievement data and provides examples of each component. Information is provided to allow school districts to conduct their own school effectiveness evaluation. Results of the California Achievement Tests form one of the bases of the analysis. The underlying question concerns whether school districts are effectively delivering instruction to students from every major social group. The most basic process that is illustrated delineates the percentage of students in each social class achieving minimum mastery. The most advanced model will demonstrate the independent and interactive relationships among social class, gender, family structure, and race. Criterion measures include standardized test results and course grades. Data are tabulated for approximately 8,000 students in grades 4, 6, 7, and 8 in the Jackson (Mississippi) Public School District. (TJH)