The two schools eventually merged in 1894.
Addey's was one of the first English co-educational secondary schools and the school still regards equal opportunities for all as a fundamental goal of the school. After the merger, Mr Slater became the headmaster in 1896, remaining head for 28 years. During this time, the present school building was opened in 1900, the south wing being added in 1933. Addey and Stanhope was originally a grammar school; it became a comprehensive in 1977. In 2004 His Royal Highness the Duke of York Prince Andrew visited the school to open the new building. The prince toured the whole school, speaking with the pupils before meeting the teachers and school governors.
The school has many old students living locally, promoting a close relationship with the local community. Founder's Day allows many past and present staff, parents and students to congregate annually to celebrate the founding of the school, a tradition observed since 1907. After the main event, held in St Alfege's Church, Greenwich, there is a celebration in the school hall with former students and staff.
The school also supports contemporary local events such as the London Marathon.
The school is considered by many to be a caring, family school with the highest expectations of all students in academic work, social skills and standards of behaviour.
The school is divided into four houses. Two are named after the founders: Addey and Stanhope; the other two are named after historical figures with local connections: Samuel Pepys and John Evelyn. Each year the four houses compete for the House Sports Cup and the House of the Year Cup which is won by the house with the largest accumulation of merits by the students in that house.
On 22 February 2006 the school became a specialist technology school, adding emphasis on the use of ICT and other modern technologies in the world; the school also receives extra funding and support for its new speciality. Joan Ruddock, Member of Parliament for the local Parliamentary constituency said:
I would like to take this opportunity to congratulate all staff and students at Addey and Stanhope School on obtaining specialist technology status. It is a wonderful achievement and will open up many opportunities in the important field of technology. I am proud of the commitment Addey and Stanhope School is showing to raising standards in education...across the borough.