Almost 50 per cent of teachers are incorrectly marking National Standards writing assessments, according to a new report for the Ministry of Education.
While 60 per cent of students who rated 'well below' in 2010 received a higher rating last year, researchers Jenny Ward and Gill Thomas say the shift in data is not completely related to student improvement.
Accuracy for judging writing assessments ranged from 3 to 89 per cent, while the accuracy in relation to maths ranged from 18 to 90 per cent.
Overall, 49 per cent of teachers' judgements on writing and 39 per cent on maths were inaccurate, based on the researchers' findings.
"Given evidence from the assessment scenarios, and the magnitude of the changes observed, it is most likely the shifts in the data are attributable to teacher inconsistency," Ward and Thomas wrote in their National Standards School Sample Monitoring and Evaluation Project 2011 report, which the ministry has recently published.
For example, a year 4 student's character description of Fred Dagg was 'above' the National Standard, but only three per cent of teachers surveyed marked it as such. Ninety-seven per cent gave it the lower rating of 'at'.
The researchers interviewed principals, board of trustees and teachers last year across 100 schools, as a basis for the fourth project report.
The teacher survey used assessment scenarios to collect information about teachers' judgments using National Standards.
Teachers use a number of sources to rate a child's achievement against the standards to provide an Overall Teachers' Judgement on them.
While the information sources used by teachers appeared to be relevant to National Standards, the individual assessments were central to the overall rating and many teachers were getting it wrong, the authors argued.
The significant variety in the accuracy of teachers' ratings was cause for concern, they said.
Ward works for the ministry's project while Thomas is an employee of Maths Technology Limited.