Almost half of all students at certain stages of education in England are still not achieving expected standards of success, a report has found.

About 43% of children are not leaving primary school having reached adequate levels of reading, writing and maths, according to analysis from the thinktank CentreForum and research body Education DataLab.

This level is set at achieving a 4b grade – sometimes referred to as a “good” level 4 – or higher in the three key subjects at the end of key stage 2, which usually lasts from the ages of seven to 11.

Forty-four per cent of pupils finishing secondary school are not achieving the national standard of five A* to C in GCSEs, the report finds. But the level of attainment has risen over the course of the past decade, the report adds, recommending a higher “new benchmark standard” to which pupils can be held.

Changes to the GCSE grading scales starting from 2017 will assess children on a scale ranging from a high of nine to a low of one, with a good pass to be considered a grade five. This falls between the current B and C grades.

Within the new system, researchers estimate the percentage of children achieving a good pass will fall to 35% in English and maths, a drop of 23%. Disadvantaged children are also closing the gap on other pupils in the classroom, the study found, shrinking as much as 30% in key stage 2 since 2006.

The same success has not been seen in the later years of secondary school, where the achievement gap is equivalent to an average of one GCSE grade in each subject. The report says this demonstrates that England still has a “system where gaps widen over a child’s time in education”.

David Laws, the executive chairman of CentreForum, said: “Our analysis shows that attainment has risen and the disadvantaged gap – notably at the end of primary education – has fallen over the last decade. This is good news, but the report shows that there is no cause for complacency.

“Almost 45% of children continue to fail to reach national benchmark standards, which are already lower than the standards reached in the best performing countries. We can also see from this report that while the disadvantaged gap has declined at each key stage, the gap still increases during a child’s time in education.

“England needs to do much better if it is to become a world leader in giving real opportunity to young people from disadvantaged backgrounds.”

A Department for Education spokeswoman said: “We welcome this report, which shows the stark choice we face in education today - either we prepare today’s young people to compete with the best in the world or we don’t.

“That’s why we’ve taken the decision to set the new GCSE ‘good pass’ at the same level as other high-performing countries set their passmark. Every time we have raised the bar for schools and colleges they have risen to meet the challenge and we are confident that this is no exception.

“Over time we expect to see more pupils reach this new higher standard and the attainment gap between disadvantaged pupils and their peers continuing to narrow.”

• This article was amended on 18 January 2016. An earlier version said that the new grading system to start in 2017 will grade students from a high of one to a low of nine. It will be a high of nine and a low of one. This has been corrected.