Park House Cheam Road, a large Victorian house was leased to the Girls' Public Day School Company in 1883 for an original period of 21 years. The first advertisements for the school appeared in the Surrey & Epsom Advertiser and the Surrey County Reporter on December 29, 1883. The first headmistress was Miss Margaret Whyte and together with her 7 assistant mistresses opened the doors of Sutton High School to 80 girls on January 17, 1884.
Park House soon proved inadequate for the needs of the 80 pupils and staff, so work began in 1885 extending the house on either side. This work was completed in 1886 and included a new assembly hall (now the Study) and a dining room. The new buildings were opened in May 1887 by Princess Louise, the daughter of Queen Victoria. Initially there was a boarding house for girls at 4 Albion Road; fees for board and lodging were £17 per term!
In 1911 Fernwood House, on the corner of Robin Hood Lane and Cheam Road was leased as a Junior School. The school was further enlarged between the wars and in 1930 the Trust bought Homestead in Grove Road and 2 years later Suffolk House in Cheam Road. The Junior school was moved from Fernwood House, housing the Upper Juniors in Suffolk House and the youngest children in Homestead. In 1935 Suffolk House was joined to the main building by the construction of the present Assembly Hall.
The school has continued to expand over the years, the library was added in 1938 and the L.E.C. Room, named after the well loved headmistress Lilian E. Charlsworth was completed in 1959. In 1970 work began on the Science block and the following year the Science and Modern languages Departments were able to move into their new home. The indoor swimming pool was built during 1971-72 and opened in May 1972. Further buildings have been added, the Garden Building was completed in 1990 and the Dene Hotel in Cheam Road was purchased and redeveloped as the Dene 6th Form Block. It was opened on June 26, 2002 by Ann Widdecombe M.P.