The mechanisms linking parental resources to their children’s opportunities are of fundamental interest to sociologists. This study is the first to provide a dynamic life course assessment of the origin–education–destination triangle using causal mediation analysis. While the age-as-equalizer hypothesis suggests that for the highly educated, direct effects of social origin are high at young ages and decrease over the life course, the age-as-stratifier hypothesis suggests that for individuals with low educational attainment, direct effects of social origin are low at young ages and increase over the life course. Findings using panel data from the German Socio-Economic Panel Study are largely consistent with these hypotheses for various measures of social origin and social destination. Overall, this study demonstrates how causal mediation analysis provides precise effect definitions that allow scholars to assess mechanisms when status transmission processes depend on educational attainment.