The project, which is being funded with support from the Scottish Government and the Scottish Futures Trust, will see a new grammar school, arts theatre and halls of residence in Kirkwall.
The division of Galliford Try will also build a primary school in Stromness and swimming pool and squash courts at the Pickaquoy Centre and three all weather pitches.
The programme will see the new facilities being built in the county over the next three years.
Under the scheme Galliford Try Facilities Management will provide a range of services for 10 years including building and grounds maintenance.