Schools are struggling to find enough specialist teachers for students with English as a second language.
Stats NZ data shows a net figure of almost 22,000 5-to-17 year olds arrived in the year to May this year.
The Education Ministry expects to add a further 371 classrooms by the end of the year, to meet roll growth.
Secondary Principals Association President Vaughan Couillault says those figures can mean a few hundred more teachers are needed.
"There's not enough teachers - full stop. You can end the sentence there, particularly in the secondary space. But at the moment, there's particular pressure on the ESOL area."
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