Children from affluent backgrounds are doing up to two hours more homework a week than those in deprived areas.
The extra hours are equivalent to three weeks of school classes and could be a vital factor explaining the better examination scores of children from richer families.
A comprehensive study gives new insight into how different communities fare in their education. The data reveals that a Year 7 pupil in a prosperous neighbourhood does more homework than a Year 10 student in a poor area. And a 12-year-old girl in a wealthier area does an hour more than a boy studying for his A-levels in a disadvantaged community.
The research is a result of collaboration between The TES and Kirkland-Rowell, a Newcastle-based school evaluation consultancy that surveys parents, pupils and teachers.
Headteachers of schools in tough areas say they are trying to make a difference with after-school sessions and guidelines for parents, but it is a battle.
Parents in deprived neighbourhoods often have no qualifications and can lack the time, skills or motivation to help their children with their schoolwork. But it would be wrong to assume that children in low-income households do not want to learn: some work part-time, while others lack increasingly important tools such as computers with internet connections.
In some homes, there is no quiet space to concentrate. Instead, children have to do their homework in the kitchen with their brothers and sisters, often with distractions such as television in the background.
The data adds to the research showing the challenges facing children in poorer neighbourhoods in getting good grades.
Government figures show low-income children who are entitled to free school meals are only half as likely as their classmates to get five good GCSEs. And a Joseph Rowntree Foundation study last year showed that disadvantaged children had a mostly negative experience of school and learning, especially when it came to finding a quiet place to study.
Kirkland-Rowell's survey reports the views of more than 75,000 parents whose children attended either a school in the most deprived 20 per cent of neighbourhoods, or one in the 20 per cent of most prosperous neighbourhoods.
It shows that on average, pupils in the wealthier areas do 5.66 hours a week of homework, while those in poor areas do 4.35 hours.
The gap is most pronounced at Year 11 - the GCSE year - when the better-off pupils do two hours more than those from poorer backgrounds. Those extra two hours add up to 78 hours a year, equivalent to three 25-hour school weeks.
In both rich and poor areas, girls do at least an hour more homework than the boys in their classes.
Mark Chaplin, managing director of Kirkland-Rowell, said the figures clearly showed the disparity between the amount of homework done by children from socially deprived areas and those from more privileged areas.
"Government policy-makers need to pay attention, because there's an inevitable link between the amount of time spent on homework and exam results," he said.
"It is still the middle-class children who are getting the university places."
Mo Laycock, headteacher of Firth Park Community Arts College in a low-income area of Sheffield, said she ensured that all her pupils had quiet space at home where they could study.
"We're not in a Dickensian society any more, with five people to a room," Mrs Laycock said. "But the important issue for me is parental support.
"Some of our parents didn't leave school with GCSEs or A-levels, and they didn't necessarily have a positive school experience, so they may feel vulnerable about helping with homework."
Where it was hard for the children to work at home, the school had a homework club every night.
Ian Clayton, headteacher of Thorpe St Andrew High in a relatively affluent part of Norwich in Norfolk, said his GCSE and A-level pupils would be expected to do more than 10 hours' homework a week.
This week, the school ran a session briefing the parents of GCSE pupils on how to set up quiet study spaces with internet connections and support their children.
"Homework is absolutely critical," Mr Clayton said. "For GCSEs and A-levels, there is no way they can get all the work done during the school day."