Maths standards achieved by New Zealand children are sliding dramatically between their fourth and eighth years at school.
Too many of the older children are failing to grasp maths fundamentals such as fractions and decimals, according to a report issued by the Ministry of Education late yesterday.
The national study of about 4000 students found only 41 per cent of those at Year 8 - mostly aged 12 - met a Level 4 or higher standard of achievement in mathematics and statistics.
The study's report, by the Government's Council for the Ministry of Education, says the students are not achieving the success expected with fractions, decimals, percentages and pro-numerals (letters used to represent numbers in algebraic problems).
Yet about 81 per cent of Year 4 students (mainly 8-year-olds) met expectations within the curriculum's Level 2 band or higher.
Even so, the report points to considerable variation in performance among children of both age groups, and says socio-economic factors are strongly associated with performance.
Students from schools of the lowest three deciles scored lower on average than those from the highest three decile schools.
Asian students scored highest on average, and Maori and Pacific youngsters performed below levels of other ethnic groups.
Despite the disappointing results from many older students, the study found teachers at both year levels indicating confidence in their own abilities, and feeling able to "engage and meet the needs" of their charges.
The teachers' confidence is belied by other reports, including results of a survey published in December which found Kiwi 9-year-olds finishing last-equal in maths among peers in developed countries
The problem persisted into high school, where officials analysing the study found "there were still students who have difficulty with the very basics, such as knowledge about whole numbers and decimals".
The Ministry of Education acknowledged in March that high school students were not being taught enough "space and shape" maths.
That followed a three-yearly evaluation of 15-year-old students' ability in maths, reading and science under the OECD Programme for International Student Assessment. New Zealand slipped from 13th place to 22nd equal in the latest evaluation.