Four secondary schools will be sharing space after two of the schools were severely damaged in the Christchurch earthquake on 22 February.
Education Minister Anne Tolley says Marian College and Avonside Girls' High are too badly damaged to open and 1700 students will be placed elsewhere.
Avonside Girls' High will share the site at Burnside High, while Marian College will share the space at St Bede's College.
Mrs Tolley says one set of students will attend in the morning, while the other school will attend classes in the afternoon. Exact details have yet to be finalised.
The Ministry of Education is working on arrangements for other severely affected schools.
Mrs Tolley says of the 121 state schools in Christchurch, engineers have cleared 76 as safe and these schools are preparing to open.