Continued expansion led in 1894 to a temporary move to a home in Palace Road to await the completion of the new building in Wavertree Road, Streatham Hill (now the location of the Junior School).

In 1938 Streatham Hill merged with (but essentially took over) the older Clapham High School (established in 1875, with Mary Jemima Alger as its first head[5]), and was renamed 'Streatham Hill and Clapham High School'.

During the Second World War some girls were evacuated from London, while others continued their schooling in often difficult conditions.

On 22 October 1952, Princess Alice, Duchess of Gloucester, as Patroness of the Girls' Public Day School Trust, opened the new Wavertree Road building.

In January 2017, a new Sixth Form Centre opened on the newly built fourth storey on the Harrison building, followed in April 2018 by a new dining hall, reception and fountain atrium.