Education union NZEI are urging schools to boycott trials of a progress and consistency tool.
The Government is planning to make it compulsory for primary and secondary schools to use the proposed computerised consistency tool, known as PaCT, and says it will help teachers with their professional judgements with National Standards.
It is not a test, the Education Ministry says.
The ministry's deputy education secretary for student achievement, Rowena Phair said PaCT has been developed in response to concerns about consistency with National Standards.
She said the tool would help teachers to know how their students are progressing and what they might need to do to support each student.