The first open air schools in Holland arose in the vicinity of sanatoria and health institutes for children recovering of tuberculosis. The 'First Dutch Open Air School' dates from 1913 and was located in the dune area of The Hague. During the twenties, lessons in the open air were deemed healthy for all sorts of children, not just the weak and ill, and a network of open air schools rapidly expanded in urban areas as well. In winter time, capes made of woollen blankets kept the children warm. These 'Eskimo-suits' were American brand.