A national evaluation has found children are better at basic maths problems but worse at more difficult equations.
The National Education Monitoring Project shows that, overall, there has been little improvement in children's maths achievement despite 10 years of special teacher training in the subject.
Its latest report says children assessed last year were no better at maths than those who were assessed in 2005.
There has been only a little improvement for Year 4 students since the first maths assessment in 1997.
Since 2000, the Ministry of Education has spent about $57 million on maths training for teachers.
It says the small improvement for Year 4 students is significant and children also have a better attitude to maths.