We estimate the effect that star students have on their siblings’ learning outcomes, measured by their high school grade point average (GPA) and their math grades. To this end, we couple administrative school data on grades with an unusual natural experiment in Peru that generates exogenous variation in the presence of star students at home. We find that star students increase their siblings’ GPA by 0.33 SDs and their math grades by 0.22 SDs. The effect size is inversely related to number of siblings, suggesting that the remaining siblings act as substitutes for the star student.