In 2005 the first Energy Efficiency Plan for South Africa was developed by the Department of Mineralsand Energy. This plan sets the target for energy efficiency improvements of 12% until 2015. Onepoint of the strategy is to improve the energy performance of public buildings like schools. Manyschool buildings in South Africa are inadequate to provide a suitable learning and teachingenvironment for students. Within the scope of this paper two representative buildings of the educationsector were analysed and assessed with regard to the construction of the building envelope and to the application of heating, air-conditioning and ventilation. Based on an analysis of the building envelope, the building service systems and of the indoor climate, various retrofit measures were evaluated and several ones realised. The effectiveness of the improvement activities were assessed by measurement series of the indoor temperature profile of retrofitted and unaltered reference buildings. The work has been performed within the EnerKey-project, funded by the German Ministry for Education and Research in cooperation with South African institutions.