At the outbreak of war, Old Danes and staff rushed to enlist and older pupils took up military drills and rifle practice. Mr Fuller volunteered as a Special Constable. The first Dane to be killed in the fighting was Bugler William Dunlop who died at Messines in November 1914 aged just 21. Twenty nine Danes would lose their lives in the war - the youngest was Rifleman W E Uglow who was just 17. Five Old Danes were decorated. They are commemorated on a plaque on the wall of the school courtyard and remembered every year as part of the school's Remembrance Day services. In addition, the school purchased twenty nine ceramic poppies from the Tower of London installation,one for each Old dane, and these are on display in the school library.

The school itself made every effort to carry on as best it could with a depleted and temporary staff and managed to maintain its academic standards. In 1915 an inspection by The Board of Education placed the school on its list of efficient grammar schools and it became eligible for government grants.

The war years were a period of shortage and economies. Paper was scarce and boys were told to fill up all blank spaces. There were two meatless days a week and meat coupons had to be surrendered for school dinners. The Houghton Street building was becoming increasingly cramped and dilapidated and there was very little playground space. The Hall had to be partitioned to form classrooms but there was no soundproofing and the classes disrupted one another.

Throughout the war, the school supported the war effort. A War Savings Association set up in 1916 collected £1,400 form the 150 pupils - a great deal of money in those days. A Cadet Corps was formed and attached to the 1st Battalion of the Royal Fusilliers with Mr Fuller as its Commanding officer. The first Harvest camp was held shortly before the end of the war when pupils went to work the land at Princes Risborough.

The only direct impact of the war on the school was a near miss from Zeppelin bombs which left broken panes of glass.

Memories of the period:

One of the school's better classrooms looked out onto Houghton Street and lessons were often interrupted by a barrel organ being played on the pavement below. The story goes that one master decided to go down and ask the musician to go away but he resumed playing a few minutes later to the delight of the boys who had bribed him to return.

The school laboratories were on an upper floor where the floorboards shook from the noise from below and made delicate experiments impossible. Paper was in short supply and school dinners were meagre. When potatoes were served for the first time in the summer term of 1916, as late as 9 July the fact was still being celebrated in the school magazine.

An Old Dane recalled Armistice Day:

"Even the youngest boys had a feeling of something unexpected to come as the hands of the clock approached eleven. The murmur of outside noises gradually changed to a roar which seemed to grow nearer as the hour struck, the wild rush to the playground, the noise of whistles, hooters, maroons and bells and the cheering and shouting of those few minutes from eleven o' clock onwards will never be forgotten"