Recent sociological scholarship on market design is ill-equipped to understand the normative and political aspects of experts’ practices in connection to political conflicts over the commodification of social rights. I develop an original approach to the politicized use of market devices to address collective concerns in a noneconomic policy field: education. When designing a high-stakes school accountability system, policymakers in Chile confronted a moral conundrum: should schools be valued according to their students’ absolute proficiency, or according to the school’s relative effectiveness? Progressive and conservative experts in charge of settling this dilemma pushed for using the statistical model (OLS vs. HLM) that yielded rankings that fit their moral preferences. Through qualitative analyses of experts’ real-world application of quantitative methods, as well as experts’ interpretations of these methods’ performative consequences, I mobilize the much-debated concept of “moral background” to unravel the conditions for subsuming ideological dissent into consensual forms of decision-making.