Founded by Sir Henry and Lady Honoria Lawrence, Sanawar is believed to be the first co-educational boarding school in the world. On the 15th of April 1847, a group of 14 boys and girls camped at the top of the foothills of the Himalayas. They lived under canvas for some weeks anxiously waiting for the first buildings to be completed before the arrival of the monsoon. Thus did Sanawar come into existence. By 1853 the school had grown to 195 pupils when it was presented with the King's Colour. One of only six schools and colleges ever to be so honoured in the entire British Empire, the others being Eton, Shrewsbury, Cheltenham, the Duke of York's Royal Military School and the Royal Military College, Sandhurst, Sanawar has held its Colour for the longest unbroken period.

From its Foundation the financial burden of the School was borne by Sir Henry until his death in 1857, when the government assumed responsibility for the finances as a mark of esteem to his memory. Under these arrangements, control of the School passed from the 'Honourable Board of Directors' to the Crown. This is a most unusual arrangement, not repeated in any English Public School.

The tradition of military training at Sanawar has always been strong and was of such a high standard that several contingents of boys were enlisted from the School and sent straight to the battlefields of the Great War. In appreciation of this, the School was redesignated in 1920 as the "Lawrence Royal Military School", and, in 1922, the Prince of Wales personally presented the School with new Colours. The School Colour continues to this day to be trooped at the Founders Celebration in early October and Sanawar pupils continue to make a major contribution to the defence of the country to this day.

Sanawar's Centenary year (1947) was crucial to the development of the School. With Independence, the bulk of the staff and children at Sanawar returned to the UK. However, the then Governor General, Lord Louis Mountbatten, presided at the School's Centenary celebrations and read out a special message from George VI. Thereafter, control of the School passed from the Crown to the Government of India, Ministry of Defence. A further transfer in 1949 brought the School under the control of the Ministry of Education and subsequently, in 1953, to the autonomous Lawrence School (Sanawar) Society. However, Sanawar retains strong links with its past. The Chairman of the Society is the Secretary for Education, Government of India and, at the recent sesquicentenary celebrations in 1997, a message of congratulation was received from the current Prince of Wales, Prince Charles.

The first Principal of the School was the Rev. W. J. Parker, (1848 - 1863). Notable events during his period include the first Founder's Day in 1849, and the opening of the Chapel in 1851. Parker was followed by the Rev. J. Cole (1864 - 1886), the Rev. A. Hilldersley (1886 - 1912) and by the fourth Principal, the Rev. G. D. Barne (1912 - 1932) who developed Sanawar into a major public school along English lines with House and Prefectorial systems, games on an organised basis and a curriculum working towards Cambridge University Examinations.

The School continued to evolve and modernise throughout the middle and later years of the last century. In 1956 Mr. E. G. Carter, retired as Principal and was succeeded by Major R. Som Dutt (1956 - 1970), the School's first Indian Headmaster. He laid the foundations for the school, as it is today, India's foremost residential coeducational public school. Developments have continued since that time, most notably under the leadership of Mr. S. R. Das (1974 - 1988).