The action is being taken on behalf of West Horndon Primary School, near Brentwood, where governors fear the publication of primary school table will paint a distorted picture for parents.
The NAHT is seeking a judicial review of the way the school's performance is to be calculated in tables to be published in March. They will show the proportion of children who achieved the expected level in tests and assessment last may in English, maths and science.
But the figures will be expressed as a proportion of the total eligible to take part, including those who were absent - so an 11 year old who missed the test through illness will still be counted as though they took the exam. West Horndon Primary is a 120 pupil village school where 17 11-year-old were eligible to take the test, but four - or almost 25% - were absent.
The application will be made by Cherie Booth QC, wife of Labour leader Tony Blair.