Councillors are due to decide on Wednesday (04) whether Nower Hill High School can build a new sixth form block.
The school, in George V Avenue, Pinner, applied to add a three-storey extension to provide new specialist space for its 300-strong body of A-level students.
Officers had recommended to Harrow Council's strategic planning committee to approve the plans for the latest scheme.
In its original submission, the school said: "No dedicated areas for facilities currently exist for the sixth form so the students are spread throughout the main school and temporary accommodation on the site, most of which does not comply with the curriculum requirements for this age group."
Within the proposed block, which hugs the three-storey gymnasium to the north of the school site, students would find eight classrooms, a study area, two computer suite, staff office, toilets and cupboards.
Solar panels are planned for the roof to provide 10 per cent of the building's energy needs.
Nower Hill High said the size of the sixth form will not increase with the introduction of the new block.
The school is part of the Harrow Collegiate, a network of 10 secondaries, two special schools, colleges and work-based learning providers that will boost the provision and quality of post-16 education in the borough.
In March last year, the collegiate won £24.7m from the Learning and Skills Council, which funds further education, to build new sixth form blocks at Harrow's high schools.
Canons High School in Shaldon Road, Edgware, subsequently won permission for its plans in April 2007, while Bentley Wood High School for Girls in Bridges Road, Stanmore, and Rooks Heath College for Business and Enterprise, in Eastcote Lane, South Harrow, received the thumbs-up in January this year.
Last month, Harrow Council granted approval for schemes at Harrow High School in Gayton Road, Harrow, and Park High School, in Thistlecroft Gardens, Stanmore.
In a completely separate project, Whitmore High School in Porlock Avenue, West Harrow, is going to be totally rebuilt as part of the government's Building Schools for the Future investment programme, leaving Hatch End High School in Headstone Lane, Harrow, as the only secular mainstream secondary school whose building plans await to be agreed.