Effectively maintained inequality (EMI) was proposed as a general theory of inequality, but the theory flows from a decades-long tradition of studying social background effects on educational attainment. After an orienting discussion of several historic challenges of the study of social background effects on educational inequality, proposed and adopted solutions to those challenges, and subsequent critiques of those solutions, we offer and justify seven principles that, if followed, produce a solid assessment of EMI. After conveying the seventh principle, two illustrative ways in which EMI addresses historic challenges with studying inequality are conveyed.Keywords qualitative inequality, theoretically focal persons, distractive control variables, EMI bounds, salient standardization Effectively maintained inequality (EMI; Lucas, 2001) was proposed as a general theory of inequality. Although EMI is resonant with theoretical resources from multiple traditions (Lucas, 2009), it most directly flows from a decades-long tradition of studies of social background effects on educational attainment. That history is composed of many path-breaking innovations and challenging realizations, reflecting a process in which each promising innovation drew critical attention that made visible its limitations, spurring further development. Understanding the historic challenges that have hounded efforts to study inequality is essential for efforts to assess EMI and perhaps other theories as well. Indeed, failure to grasp those historic challenges not only may