Reducing underachievement in basic skills and Early School Leaving (ESL) rates is at the core of the strategic and political priorities for the European Commission. This has become even more critical in a post-pandemic era where students coming from lower socioeconomic status, refugees, migrants, Roma, etc. are not reaching the competencies to thrive in life. SCIREARLY is determined to identify, systematize and replicate successful policies and practices based on scientific research that has proven to reduce underachievement in basic skills, including digital skills, while fostering psycho-emotional aspects and well-being. This know-how will contribute to reducing ESL in Europe, enabling upward social mobility for the most vulnerable groups. To this aim, SCIREARLY will (1) examine the determinants, including the influence of high-quality early childhood education and care (ECEC) in learning outcomes (2) measure and verify the impact of these determinants on vulnerable groups, identifying successful pathways to overcome it (3) map and replicate most successful practices in addressing low achievement in basic skills (4) develop a framework and an instrument for diagnosis and enhancing the quality of ECEC to leverage quality learning outcomes for primary and secondary pupils (5) analyse and propose transferable and scalable political measures that have proven to reduce ESL. As a result, SCIREARLY will provide evidence-based findings to recreate and scale up optimal learning environments reducing underachievement from a preventive perspective, especially for vulnerable groups; this will be done from an interdisciplinary approach and mixed-methods design including multilevel, quasi-experimental, and life course perspectives. The project relies on a participatory and dialogic approach that promotes the co-creation of scientific knowledge and solutions among educators, students, families, scientists and policy-makers, ensuring the societal impact of the project.