The job involves construction of a five-storey extension, including three storeys in a basement below ground level.
The new facility will include a sports hall, flexible performance space, drama studio, and dance studio.
Interserve started demolition of an existing gymnasium and assembly hall this month, with piling works and excavations soon to follow for the construction of the deep basement.
The building will be clad with full-storey-height planar glazing, brickwork and copper cladding for the second floor dance studio.
The BREEAM target for the project is ‘Very Good’. The new NHEHS arts and sports facility is scheduled to be completed in November 2012.
John O’Neill, area manager for Interserve, said: “We will create a modern, 21st century learning environment, while allowing the existing school to operate as normal.
“During the construction phase, we are planning curriculum activities with NHEHS students, such as art and design competitions, and creation of a project blog.
During the past two years Interserve has delivered over £400m-worth of schools projects and recently started work on Langley Hall Primary Academy in nearby Slough, one of the first schemes under the government’s ‘free schools’ initiative.