The two-storey timber frame building will house a new hall, dining room, kitchens, classrooms and has been designed to be constructed off site.
Hailed as a 'fast-track' scheme, the project was given the go-ahead by Westminster Council in June and is due to open in Autumn 2006.
Explaining the development, the London-based practice said: 'The design has a predominantly glazed and open ground floor, with coloured panels around the serviced areas. The upper floors are wrapped in oxidised copper.
'The outdoor playground and indoor hall can feel like one large space, with the existing nature area to the east almost spilling into the hall.'