Principals say Christchurch parents need to get their children back to class.
The Government says some students have not been back to their school since the earthquake on 22 February and have not enrolled anywhere else.
It is not certain how many children are still not attending school, but it is believed students are absent from each school in the damaged parts of the city.
Many schools, especially primary level, have fewer students since the 6.3-magnitude quake hit the South Island city.
More than 6500 of those missing children are enrolled at other schools, most of them in other parts of New Zealand. But the Government says some children are not going to school anywhere.
Principals say some families do not want to enrol their children in a school until they have decided where they will live.
Canterbury Primary Principals Association president John Bangma says his own school has five or six children in that situation and expects most schools in damaged parts of the city will also have some as well.
However, principals say it is important that parents get their children back to school - even if they have to change within a week or two.
Schools are required to report non-attending children to the truancy service after 20 working days.