Border Construction has gained a £20m contract to redevelop Trinity School in Carlisle.
The multi-million pound makeover is expected to take the Carlisle-based building firm two years to complete.
Parts of the school's original architecture will be retained during the work, following consultation with students, staff and parents, who will arrange a series of meetings with local residents over the next month about its full design.
It means some of the site's historic buildings, such as the Carliol building, or Carlisle Grammar School, and the old Creighton and Margaret Sewell entrances to the school will be retained.
Work on the finalised design is expected to begin in May next year, with a completion date set for spring 2012.
The work comes as part of a £80m reorganisation of schools and colleges in the city.
The Richard Rose Central Academy, on the former St Aidan's School site, is to undergo a £30m refurbishment, along with a £5m Kids Zone. Further funding will be spent on redeveloping Carlisle College, and work on a new £2m sports complex at Newman College continues.