The union for primary school teachers is advising primary and area schools not to release their national standards results to media.
The NZEI says it issued the advice to its members after the Dominion Post newspaper asked schools in the Wellington region for the data under the Official Information Act.
Union president Ian Leckie says media may create league tables with the data, to compare schools, but says that would be misleading, because every school's interpretation of national standards is different.
Mr Leckie says the union fears sensationalist headlines based on misleading data.
He says says schools can refuse the Official Information Act request on the basis that the Ministry of Education will be releasing the information later this year.