Although a school has been on the Prep School site since 1861, the history of Downsend in print dates back to 1891. In the census of that year the school was owned by a Mr Johnson, before being purchased by Arthur Howard Lindford in 1918 who amalgamated the school, and its one pupil, with his own school, Peterborough Lodge.

Previously in Hampstead, Peterborough Lodge had flourished as a boys only school for over twenty years; even through World War One. With the school’s history steeped in family traditions, Arthur’s son Cedric joined his father in 1921 and worked in the school, ultimately as Headmaster, until his retirement in 1968. New developments were added as the school continued to grow; the cricket pitches and senior school building (now dining hall) were added in 1927 & 1930 respectively, before the junior school was built in 1934. During the Second World War, a number of boarding pupils were evacuated to Hurstpierpoint College under the leadership of Deputy Headmaster, Denys Straker. During this increasingly threatening time, the newly purchased Ermyn Way House, planned as a nursery school, was destroyed by a 'doodle-bug' bomb in 1944. Despite this the school, surprisingly perhaps, grew in numbers during the war.

Post war, the school continued to expand and by 1950 had reached over 200 pupils. It was at this point that Cedric Lindford took over the reigns as Headmaster. Following his retirement, the family tradition continued under its new joint Headmasters, Christopher Lindford and Denys Straker. This coincided with boarding at Downsend being discontinued, but significant improvements to the school’s infrastructure were implemented, commencing with the introduction of a new senior school building, which opened in 1968.

In 1979, the first Downsend Lodge (Leatherhead) was opened as a pre-prep, which catered for girls up to the age of 13. By 1987 two further Lodges (Epsom and Ashtead) were added, with girls being accepted onto the main site in 1988 (although initially taught separately).

Within three years a new Sports Centre had been added. However it was only in 1997, with the construction of the new junior school building, that girls were fully integrated into Downsend to create the co-educational school that Downsend is today. The Lindford family finally sold the school to the Asquith Court School Group in 2002, with a roll of approximately 550 pupils, before its current owners, Cognita, took control in 2004.