In post-industrial societies, a college education is the main channel for upper classes to prevent their children falling down the social ladder, while, for working classes, it is the best bet for upward mobility. Despite attaining post-compulsory education was equalised and a driver of social mobility in the last decades, inequalities by socioeconomic status (SES) in college graduation, the main social lift, remained relatively unchanged. We are only starting to understand the complex interplay between biological and environmental factors explaining why educational inequalities gestate before birth and persist over generations. Besides, further research is needed to unravel why advantaged students are more likely to get ahead in education than equally-skilled, but disadvantaged peers.  This thesis bridges interdisciplinary literature to study how parental SES affects educational attainment during childhood in Germany, evaluating the implications for social justice. It contributes to the literature by (1) analysing the consequences of prenatal health shocks on skill formation; (2) examining the effect of cognitive and non-cognitive skills on the transition to secondary education; and (3) assessing SES-heterogeneity in these associations. Drawing from compensatory theories, I demonstrate how negative traits for educational attainment—low birth weight and cognitive ability—are less detrimental for high-SES children from the early stages of the status-attainment process due to mechanisms like parental investments and aspirations, and teachers’ bias in assessments.  The German educational system enforces early tracking into academic or vocational pathways from age 10, supposedly according to ability. Thus, the case of Germany represents an institutional starting gate to evaluate equal opportunity, where compensating for negative traits might be difficult. To test compensatory theories, I utilise the Twin Life Study and the National Educational Panel Study applying quasi-causal empirical designs. The findings challenge the liberal conception of merit as the sum of ability plus effort in evaluating equal opportunity.