Learning to read in the first grade is essential for reducing educational inequalities, highlighting the need to evaluate and enhance reading programs. This study examines "Plan Leo Primero," an innovative national initiative to ensure that all first-grade students in Chile effectively learn to read and comprehend texts. A total of 715 educational stakeholders—including principals, technical leaders, teachers, and guardians—participated in the evaluation, which used validated questionnaires across two regions of the country. The study employed a quantitative and descriptive methodological approach to evaluate the implementation process of the program, fidelity, and impact on literacy outcomes. Despite challenges posed by the COVID-19 pandemic, such as reduced student attendance, shorter implementation periods, and limited resources, the findings indicated successful program implementation with significant improvements in first-grade literacy. Key results included high acceptance and frequent use of the program's instructional guides and pedagogical tools by teachers, widespread adoption of structured methods aligned with cognitive theory, enhanced teachers’ digital competencies, and strong engagement from guardians in reading activities. Grounded in action theory, the study emphasizes the alignment between program strategies, stakeholder participation, and systemic actions, fostering sustainable literacy progress. The process evaluation identified areas for improving program fidelity, demonstrating that structured evaluation frameworks ensure robust implementation and open avenues for future research. Future projections include assessing the use of technology and communication tools and promoting the social appropriation of knowledge among all stakeholders to drive inclusive and impactful literacy reforms in Chile and the broader Spanish-speaking world. © 2024