Civil Defence says all schools in Christchurch city, Selwyn and Waimakariki districts remain closed on Wednesday.
Director John Hamilton says some schools might reopen on Thursday, but that is a decision for each board of trustees to make. He says trustees must consider the safety of the schools when deciding whether to reopen.
Parents are advised to contact their own schools for specific information about the situation there.
Education Minister Anne Tolley says some schools may be able to open on Thursday, but not many. She says two-fifths of schools inspected so far need further structural analysis.
The Education Ministry must sign off schools and early-childcare centres as structurally safe before individual boards of trustees can resume control.
Boards then have a responsibility to look at matters such as water supplies, sewage and staff numbers.
The minister says relief teachers and prefabricated classrooms are being sought nationwide.
Aftershocks are damaging some schools that were previously structurally sound.