The rapid digitalization of education has reshaped learning environments but also exacerbated longstanding social inequities, creating a multidimensional digital divide. This study examines the structural determinants of digital exclusion, differences in access, skills, and usage, and evaluates their influence on students’ academic performance. Using a mixed-methods design, we analyze micro-level data from the 2018 Program for International Student Assessment (PISA) alongside a thematic synthesis of recent case studies. Quantitative results show a strong positive association (p < 0.01) between a composite Digital Access Index and achievement in mathematics, reading, and science, independent of socioeconomic status. The qualitative findings reveal three recurring determinants: socioeconomic and infrastructural constraints, disparities in teacher digital preparedness, and variations in sociocultural and digital capital. Integrating both strands of evidence, the study demonstrates how digital exclusion contributes to persistent educational disadvantages and constrains long-term opportunities in higher education and the labor market. Our study that addresses the digital divide requires coordinated reforms targeting infrastructure, digital competency development, and equitable pedagogical design to prevent the further entrenchment of digital stratification.