School sports is not only a compensation for inactivity but also training and basic experience in many kinds of sports. The stress exercised by school sports is similar to that of hobby sports. The dimension of errors in respect of excessive stress in orthopaedic diseases and the biological development--acceleration/retardation--is important for prohibiting school sports in some diseases. The indication for prohibiting school sports either completely or incompletely in the most important orthopaedic diseases in childhood, is discussed. The special importance of part prohibition or participation without any giving marks, is emphasised.