 The County School, Hendon opened as a fee-paying school of 350 pupils in September 1914, just a month after the outbreak of the First World War.By 1927 the field at the back of the school was levelled and trees planted, and in 1929–1930 the building of the Gymnasium was started.In 1931 the intake of pupils rose from a two form entry to a three form entry, and by 1932–3 the extension on the north side of the original school building was finished to enable accommodation of 480 pupils.