This paper illustrates the influence of a new national assignment system (NSAS) on Chilean middle-class advantage. This system was designed to increase educational equity by changing the previous school admission "rules" that were prejudicial against low-income students. We use Bourdieu's conceptual tools, drawing on concepts of capitals and field, to analyse the influence of the new rules of the game on the value of middle-class capitals. To understand how the new rules shape middle-class families' advantages, we link qualitative and quantitative analyses that empirically explore how families subjectively interpret the policy change and how objectively it shapes their access to desired schools. The qualitative phase shows that middle-class parents experience the NSAS as a risky new scenario. However, quantitative analysis shows the NSAS is associated with only a modest decrease in middle class-advantages. We illustrate the difficulty of transforming marketized educational systems, where previously privileged families react against equity-driven changes.