Contractor Interserve will redevelop Rainford High Technology College near St Helens after the Co-operative Bank provided a £33m, 27-year loan to finance the project.
The college will get 150,000 sq ft of new and refurbished space which Interserve will then maintain.
The project was among those saved from cancellation by Education Secretary Michael Gove after he reviewed the Building Schools for the Future programme.
Barclays European Infrastructure Fund has also contributed towards the cost.
Interserve also won a design-and-build contract for De La Salle School in St Helens under the BSF programme, with the two contracts having an aggregate construction value of about £48m.