Education Minister Anne Tolley appears to be downplaying NCEA achievement figures to boost support for standards set by the Government.
She says school-leaver statistics issued by the Ministry of Education show the need for National Standards to lift achievement levels.
Radio New Zealand's education correspondent says the ministry's annual school sector report shows the biggest ever improvement in qualification rates.
However, Mrs Tolley says nearly one in five school leavers failed to achieve NCEA Level One or above in 2008.
The school sector report shows 16% of students left without a qualification last year, compared with 18% in 2007 and 25% the previous year.
From next year, the progress of all primary school children in maths, reading and writing will be measured against standards set by the Government.
The Post Primary Teachers Association says Mrs Tolley's comments do not acknowledge huge gains have been made, particularly from the days of the old School Certificate system when 50% of students left school without any qualification.