We investigate the extent to which families can offset the adverse effect of a young school starting age (SSA) on children’s educational attainment and how this relates to institutional features of the education system. We hypothesize that parents’ ability to compensate for an early educational disadvantage of their offspring may be a function of the selectivity of an education system. To test this hypothesis, we study the causal link between SSA and the likelihood of students being placed in higher tracks in lower secondary and academic tracks in upper secondary education in Switzerland. We investigate the extent to which parents from different socioeconomic backgrounds can mitigate this early educational setback, considering resources such as parental education, occupation, and income. The findings indicate that a lower SSA reduces the chances of students entering advanced tracks, although this impact diminishes as they grow older. Concerning parental resources, highly educated parents compensate for a young SSA only during the first transition to lower secondary education, a point with relatively low educational selectivity. In contrast, during the second transition to upper secondary education, a point at which the education system exhibits higher selectivity, there is no compensation by parental education and, thus, rather support for a boosting advantage model of educational attainment. These findings demonstrate that parents’ ability to compensate for an early educational disadvantage varies with the selectivity of an education system.