On 16 February 2005 the Kyoto Treaty enters into force. On that day the schools decided to put some symbolical attention to this treaty and put the heating at school at least one degree lower and stimulated students and teacher to wear warm clothes that day. This was their contribution to the Kyoto agreement. The schools organize various educational and leisure activities to raise awareness among their students, teachers and other school staff and to ensure an energy efficient school. Sustainable energy is the real message of the thick sweater day. Reducing energy also means reducing greenhouse gas emissions.