Plans to expand Notre Dame RC Girls' School in St George's Road have been approved by Southwark's planning committee.
Last Tuesday Southwark's planning committee considered an application to build a new year 7 block on part of the car park at the front of the school, including five new classrooms and a dining area.
The extension has been designed by Cottrell & Vermeulen and is part of the Southwark Schools for the Future project.
"The building has a deliberately contemporary design and will be built in brick as a direct reference to the main school building," explained planning officer Bridin O'Connor.
"The window openings are arranged in a slightly random manner which gives the building its character."
Ms O'Connor explained that three trees would be felled to make way for the new building, including a large London plane tree.
She said: "Its loss is regrettable but having examined all options for providing this much-needed accommodation, officers are satisfied that there is no alternative."
The tree has been valued at £36,000 and up to 10 semi-mature trees will be planted along St George's Road to compensate.
The school's headteacher, Sister Anne Marie Niblock, addressed the committee to explain why the new building is needed.
"Our students achieve in spite of the restrictions of the building which is congested, does not have enough classrooms, provides no dedicated outdoor recreation space and has inadequate dining facilities," she said.
She explained that the new buildings would provide facilities for wider community use, including adult education, meetings and social events.
"The school is rooted in history and tradition, yet it embraces all that is good in modern approaches to education.
"We believe that the architecture which is proposed reflects this ethos as the design uses traditional materials but reinterprets them in the modern composition."
The committee also heard from Cathedrals ward councillor Adele Morris who spoke in support of the planning application. "It would be a great shame to let a tree stand in the way of a fantastic school being able to improve its offer to young people in our borough," she said.