The buildings’ interior spaces present significant variations of temperature, due to the absence of insulation, resulting in big energy losses during winter and overheating during the summer period. Therefore it was necessary to transform their exterior shell, in order to remedy all problems of inadequate heat / sound insulation, poor ventilation and defective windows. The three buildings were fully insulated on the outside by extruded polystyrene panels and brick cladding, while all of the existing windows were replaced by double pane insulated windows, in order to reduce energy losses. The roofs were reconstructed by re-using the existing materials (wooden structure, roof tiles), after the installation of appropriate thermal and moisture insulation materials. New windows were opened on the northern facades to provide for cross-ventilation in order to avoid high temperatures during the summer. Permanent metal shades were specially designed for the southern facades for further solar and glare protection of the openings. The installation of a sound-absorbing acoustic tile ceiling reduced the reverberation problem experienced in the classrooms.