The government has decided to move Blenheim's two secondary schools to a new, shared site at a cost of $63 million.
Education Minister Hekia Parata said Marlborough Girls' College and Marlborough Boys' College will be moved to a new location in 2021.
A shared site would allow the schools to share specialist facilities and make it easier for them to work together, she said.
Marlborough Girls' College principal Karen Stewart said the government's decision to move the school to a new location with Marlborough Boys' College was fantastic news.
The change was prompted by property problems at the schools, she said.
Though some local people thought the schools should merge into a coeducational school, most wanted them to remain separate, Ms Stewart said.
Marlborough Boys' College principal Wayne Hegarty said the move was not the cheapest option but the new schools would be future-focused.
The future of the schools has been under consideration for several years.
The schools' new location has yet to be purchased.
Today's announcement ends several years of consultation about the future of Blenheim's colleges, and is the latest in a series of multi-million-dollar school rebuilds and redevelopments announced in the past month.
Other options considered included keeping the schools where they are, or merging them to form a new, coeducational school.