This study presents a comprehensive comparative analysis of school building stock in Italy and Greece, focusing on the cities of Padua and Volos. The research, part of the ongoing SchoolNet FSE project, aims to bridge the gap in comparative studies between different European contexts and develop strategies for energy-efficient renovation of school buildings. The methodology involves a three-level analysis: national overview, detailed case studies of Padua and Volos, and an in-depth examination of a specific school building in Volos. The study reveals that both countries face similar challenges, with over 60% of school buildings constructed before the introduction of stringent energy efficiency regulations. Significant differences in building distribution, morphology, and management reflect diverse educational policies and approaches to space optimization. The Greek case study demonstrates the potential for substantial energy efficiency improvements through targeted interventions, with an estimated 48.7% reduction in the annual primary energy consumption. The research highlights the importance of adapting renovation strategies to local specificities while considering energy efficiency, occupant comfort, and educational opportunities. It also emphasizes the potential of integrating technologies like green roofs and photovoltaic systems to transform school buildings into educational tools for sustainability. This study provides a foundation for developing targeted energy renovation strategies in the school building sector, contributing to the European Union's sustainability goals and promoting environmental awareness among future generations.