In 1885, a school was founded in some shophouses in Tanjong Pagar by Mr Gan Eng Seng to offer free education to the children of poor parents in the vicinity. It was called the Anglo-Chinese Free School.
No school perhaps has had a more distinguished array of personalities connected with it than Gan Eng Seng School. Before it became a government school, it had on its Board of Trustees illustrious names as Tan Keong Saik, Ho Yang Peng, Wee Theam Tew, Lee Cheng Yan, Chan Sze Jin, Wee Swee Teow, Song Ong Siang, and Dr. Lim Boon Keng.
When in 1889, the Government gave the school a site in Telok Ayer Street for a new building, it was Mr Gan Eng Seng who put up the building. On 4 April 1893, the new building was officially opened by the Governor, Sir Cecil Clementi Smith.
English and Chinese were taught at Gan Eng Seng School until the founder’s death when it became a purely English School. Then, owing to financial difficulties, it no longer functioned as a free school and for some time fees were charged.
In 1937, the Board of Trustees, owing to financial difficulties, was not in a position to carry out major and urgent repairs to the school premises. Therefore, in the interest of the school, Gan Eng Seng School became a Government school in 1938.