Children in their first two years of high school are being left behind, an Education Review office report finds.
An ERO report of junior classes in high schools shows only seven per cent of schools are effectively assessing and improving student achievement in maths and literacy in years 9 and 10.
ERO visited 68 secondary schools in 2011 as part of its regular reviews of schools and found little information was being gathered by schools on pupils in years 9 and 10.
The report found those years were being left behind in literacy and mathematics.
ERO chief review officer Dr Graham Stoop said secondary leaders and teachers urgently needed to improve using literacy and mathematics assessment information for planning, implementing and reviewing the curriculum for all children in years 9 and 10.
He said it was critical for those not achieving as well as they should - Maori and Pacific pupils, children with special needs and those from poor backgrounds - get an education that prepared them for working life.
BusinessNZ chief executive Phil O'Reilly junior class performance often determines what subjects pupils can take and their chances of success in later schooling.
"By the time young people reach year 11 - NCEA level 1 - it may be too late to do the remedial work that should have been done in the junior years."