Most of the persistent low achievers in England's schools are poor and white, and far more are boys than girls, a Joseph Rowntree Foundation study says.
The researchers say some policy initiatives have lost their way
Chinese and Indian pupils are most successful. Afro-Caribbean pupils do no worse than white British from similar economic backgrounds, results suggest.
The analysis, by London School of Economics academics, says that some policies are having positive effects.
But others, such as school league tables, actually make things worse.
The authors, Robert Cassen and Geeta Kingdon, analysed official data, focusing on four measures of low achievement:
- no passes at all in GCSE/GNVQ exams
- no result better than grade D
- no pass in either English or maths GCSE
- not getting five GCSEs including English and maths at any grade
Prof Cassen also visited schools and colleges and interviewed educationists and council officials.
The chief characteristic of low achievers is that they come from disadvantaged backgrounds.
They are more likely to qualify for free school meals, live in areas of high unemployment, and have single parents who themselves have poor qualifications.
Children with special educational needs and those in local authority care figure prominently.
Not speaking English at home, however, is "a short-lived handicap", overcome by most youngsters by the time they are in secondary school.
Schools do make a difference - though only about 14% of the low achievement can be attributed to school quality, the report says.
Disadvantaged students are more likely to be in worse-performing schools, and measures to promote fair selection will help.
But there is considerable variability between schools and between local authorities.
Case for change
The researchers say the policy implications are that progress is being made, but some policies are not implemented as well as they should be - for example, those to help special needs and cared for children.
"No child deserves a worse teacher for any reason, least of all because he or she may not help a school reach a target."
The researchers say the government attainment target of five GCSEs at grade C or above, and associated league tables, "do a disservice to potential low achievers".
The latest incarnation of the national literacy strategy is out of step with current research and "there is a case for changing it".
"It appears to have been introduced without rigorous attention to the findings of research about the teaching of reading."
They express doubts about the focus on synthetic phonics - just as a new teaching system centred on this is being promoted to primary schools by the government.
And they say funding is not always directed to where it can help most.
"Giving far greater priority to reducing low achievement would represent money and effort well spent, for the individuals concerned and for society at large," the report concludes.
Schools minister Jim Knight said: "Boosting achievement for low achieving groups is at the heart of our education reforms and we are delivering a curriculum and school experience to better engage boys.
"We have invested over £1bn to support personalised learning, with special weighting for deprived areas, to ensure that low achievers are helped to catch up and do not fall further behind."
The government was also providing one-to-one tuition for 300,000 pupils in maths and 300,000 in English to help low achievers.
"In recent years, the proportion of white boys eligible for free school meals achieving five good GCSEs has improved faster than the national average."
National Union of Teachers leader Steve Sinnott said: "The foundation has identified the impact of social deprivation on all young people's achievement.
"Its conclusions are straightforward common sense which should be adopted by the government."