There is an ever-growing emphasis worldwide on increasing access to early childhood care and education programs and generating high-quality educational experiences for children, especially those from low-income families. Chile is not an exception in this global trend. Although Chile has significantly expanded early education coverage for children from low-income backgrounds, there has been little research to assess the effects these programs have had in improving academic outcomes. Responding to this need, this study assesses the impact of Chile's public early childhood education programs on fourth-grade academic achievement (as measured by the country's national Education Quality Measurement System, SIMCE). Our results indicate that, after controlling for socio-demographic factors potentially associated with choosing to participate in an ECCE program or not, ECCE is positively associated with academic gains on all three SIMCE tests: mathematics, reading, and social sciences. Chilean children who participated in public ECCE programs scored on average 0.23 Standard Deviations (SD) higher in math, 0.19 SD higher in reading, and 0.19 SD higher in social sciences than children who did not attend an ECCE program before entering Kindergarten. However, our findings suggest that not all children benefit equally from attending ECCE. Results show that boys benefit academically significantly more than girls, and that the ECCE effect on academic achievement also differs depending on the Socioeconomic Status (SES) of the families, with children from middle-low SES groups benefiting the most. (author abstract)