Cultural reproduction and cultural mobility, two mainstay theories accounting for the role of cultural capital in educational inequality, differ from each other in the way cultural capital is hypothesized to mediate the relationship between family background and educational outcomes (the mediation mechanism) and in the differential returns to cultural capital by family backgrounds (the interaction mechanism). By explicitly specifying such mediation and interaction mechanisms in a triangle model, this article presents an approach to decomposing the total dynamics between family background, cultural capital, and educational outcomes into four theoretically ridden components. This analytical framework is illustrated with cross-national data of the Programme for International Student Assessment (PISA), which facilitates the comparison between possession and activation of cultural capital, enriches the typologies of cultural reproduction and cultural mobility, and quantifies the explanatory power of cultural capital for the overall educational inequality.