<p>School buildings play a vital role not only in education but also as key public infrastructures influencing community well-being and environmental performance. This study assesses the energy performance and retrofit potential of nine public school buildings in the Athens metropolitan area, constructed between the 1970s and 1990s. These buildings, embedded in the dense urban fabric of Attica, exhibit significant energy inefficiencies due to outdated envelopes, poor insulation, and obsolete HVAC and lighting systems. Data analysis reveals that existing schools consume substantially more energy than reference buildings, with high heating, cooling, and lighting demands leading to elevated operational costs. Three retrofit scenarios were evaluated to measure potential improvements. Scenario 3, representing a deep and integrated retrofit strategy, achieved the most substantial results—delivering over 70% reductions in energy consumption and operational costs on average. In several cases, Scenario 3 outperformed even the benchmark reference buildings, highlighting the effectiveness of comprehensive retrofit packages. The study also contextualizes these findings within the evolving Mediterranean climate, where prolonged heatwaves and an extended warm season increasingly overlap with the school calendar. Schools are particularly vulnerable to overheating due to high occupancy during peak temperature hours, affecting thermal comfort, student health, and academic performance. Overall, the findings underline the urgent need for deep energy retrofits in the educational building sector. Such interventions offer significant cost savings, improve indoor environmental quality, and contribute to broader national and EU climate targets. Given the societal importance and scale of the public school network, investing in these upgrades is both a strategic and necessary step toward energy resilience, sustainability, and enhanced educational outcomes.</p>