Using administrative data for Chile, we study the impact of School Starting Age (SSA) on the characteristics of the school of first enrollment. After addressing the usual concerns of endogeneity using minimum age requirements and an RD-design, we uncover gains associated with a delay of school entry at the start of the student's school life. SSA is associated with an enrollment in a school with an approximately 0.1 standard deviations higher average in standardized test scores, an increase of approximately 0.17 years in the average education of the peers' parents, and an increase of 4 percentage points in the probability of being enrolled in a private school. The heterogeneity analysis by parents' education reveals the largest gain in the probability of enrollment in a voucher school among less-educated families. We also show that the impact on school's standardized test scores occurs among girls. This heterogeneity by parents' education and student's gender differs from that reported in previous studies.