This manuscript describes the weaknesses of using average and median test scores and proficiency-level indicators and the advantages of using value-added indicators in measuring the performance of schools, programs, and policies.  Meyer stresses that average test scores used as a variable to measure student achievement, is “contaminated” by factors aside from school performance, including student, family, and community characteristics.  Value-added modes have the option of examining these other factors and separating them in the statistical model.