Historic achievement gaps in mathematics favoring male students have recently started to narrow, close, or even shift in favor of female students. Still, in many countries, male students continue to outperform their female counterparts in international mathematics assessments. Chile has one of the highest mathematics achievement gaps in the world, as shown by international assessment tests, with males outperforming females. Using nationally representative longitudinal data and multigroup latent growth modeling (LGM), the purpose of this study was to track the gender scoring gap in mathematics from kindergarten to grade 12. Findings showed gender differences emerged during preschool and increasingly widened as students progressed through school. Although the gap subsided slightly between grades 10 and 12, the initial gap almost doubled by the end of high school, with important implications for access to higher education and choice of major.