The figures remained largely unchanged over three years, rising an average 1 per cent across all year levels since 2012.
Chief Education Scientific Adviser Professor Stuart McNaughton said experts knew many of the reasons why children were falling behind and were already acting on those, but urged that more could be done to lift achievement.
"The number we have set isn't 'magic'. In principle we should be able to get a higher proportion of students up to the standard."
Professor McNaughton said a 1 per cent gain meant up to 4000 more students reaching the standard each year. A small, incremental increase across a large system was still a positive, he said.
The Herald will this week explore what more could be done to lift results, with an investigation finding system-wide issues, including:
• Despite pumping billions of dollars into early childhood education, there has been no national effort to collate data on whether children's early literacy and numeracy has improved
• Students entering teaching college tend to have lower marks than those across other degree-level courses; and the overall numbers studying teaching have dropped
• Not all schools had the capability to take up ministry interventions for underachieving students, with some "overwhelmed" by the levels of underachievement.
The Herald will also examine patterns in the National Standards results, which was able to be evaluated as a trend for the first time with the publication of three years of in-depth data. Analysis shows significant variability across subjects, and by gender, ethnicity and socio-economic status.
Educators say the minimal level of improvement raised questions about whether the hugely controversial National Standards initiative has worked as intended.
"It bears out what the profession said at the time - that the standards wouldn't be enough. They give us a broad look at where a child sits within an age group but don't tell us what their strengths and weaknesses are or what to do next," said long-time primary school principal Frances Nelson.
"It hasn't become critical to teaching and learning. It hasn't been the silver bullet. So why spend all that money on something we didn't need?"
National Standards was an integral part of John Key's 2008 election campaign, where he pledged to raise achievement by requiring schools to clearly set out expectations, and to report that clearly to parents.
The standards, in which teachers use a four-point system to rank children from "well below" to "above", were widely contested by the sector at the time but are now mandatory in all schools.
Education Minister Hekia Parata said she expected more progress as the standards bedded in, and as the new Communities of Learning, where schools cluster together to address achievement issues, got under way.
While the percentage increase was not large, the improvement was "extremely meaningful" for the kids involved, she said.
"I am never satisfied with progress. I always want to go further, faster because I want all our kids to get the best education possible, but we have to recognise that National Standards is still in its infancy," she said.
Chief executive of the Education Council, Graham Stoop, said although National Standards had not "failed" it could have been more successful if there had been more collaboration and support for teachers.
"We will see improvement over time. Right now though, we need to change the discussion from what the level of achievement is, to how to accelerate progress for all learners."
Read more:
• The Primary Issue: National Standards - why aren't they working?
• The Primary Issue: Quality of school report cards a 'lottery'
The figures at a glance
• Pass rates lifted an average 1 per cent across reading, writing and maths over the three years to 2014
• Writing had the lowest proportion of children at the standard, with 71 per cent achieving at or above expected levels. Maths had 75 per cent and reading 78 per cent. The Government target is 85 per cent.
• Maori and Pasifika students made slightly larger gains than the average - between 2 and 3 per cent over the three years - but lagged by up to 20 percentage points behind their Pakeha and Asian peers.
• Boys were, on average, eight percentage points behind girls.
• The largest differences were between the rich and poor. For example, only half of children at a Decile 1 school had the required maths competency by their last year, compared to 80 per cent at a Decile 10.
• There was a drop-off in achievement after Year 4 across all subjects, matching trends identified in other national and international surveys
The series
• Day 1: National Standards: A failed crusade?
• Day 2: Measuring the success of Early Childhood Education
• Day 3: Teacher quality: How to raise the status
• Day 4: The problem with maths
• Day 5: Peace, war and reading