Leading educationalists are united in opposing the introduction of league tables ranking the performance of primary schools.
More than 100 academics have signed a letter to Education Minister Hekia Parata.
Prime Minister John Key says league tables based on National Standards data are a good way for parents to get information on how schools are performing.
But one of the signatories, Lester Flockton of Otago University, says the tables would be deeply flawed and misleading.
He says a person's height and weight can be measured with a degree of accuracy, but measuring a student's literacy and numeracy - which is much more complex and variable - is far more difficult.
Mr Flockton says the best way for parents to assess a school's performance is to read its Education Review Office report and talk to other parents with children at the school.
Professor Martin Thrupp of Waikato University told Morning Report the tables are based on inadequate data and can cause real damage to schools.
He said schools can be led into giving more attention to some students than others to help boost their placings on the League Tables.
Letter not yet received
Education Minister Hekia Parata says she has not received the letter yet and can go only by what's been reported.
She says there needs to be a more informed conversation about how data on achievement is used.