Clever, poor teenagers are almost half as likely as their richer classmates to study, and get good grades, in the A-level subjects that will help them gain places at the UK's top universities, a study shows.
They are also much less likely to get three A-levels in any courses.
Research suggests that going to a decent nursery, reading for pleasure, attending an outstanding school, taking part in school trips and doing homework every day can boost a disadvantaged pupil's chances of getting good results.
The study, by the Department of Education at Oxford University, is based on data drawn from more than 3,000 young people who have been tracked from the age of three for the Effective Pre-School, Primary and Secondary Education (EPPSE) project.
Researchers found that just a third (33%) of bright but disadvantaged students took one of more A-levels in so-called "facilitating" subjects, compared to 58% of their wealthier peers with the same academic ability.
These are the subjects required most often by Russell Group universities, considered among the best institutions in the UK. They include English literature, maths, physics, biology, chemistry, geography, history and languages.
Less than a fifth (18%) of the poor students followed gained at least a B in these subjects, compared to 41% of their advantaged classmates.
The findings also show that just over a third (35%) of the sixth-formers identified as clever based on their test results at age 11 got three A-levels in any subjects, compared to 60% of their high-achieving, richer peers.
An analysis of the data found that sixth-formers who did two to three hours of homework each night were nine times more likely to gain three A-levels than those who did none.
"Spending time on homework is likely to reflect both student motivation and engagement, study skills and independence, school policies and the priority teachers attach to encouraging students to study at home (or provide opportunities after school), as well as parental attitudes and support," researchers said.
The study concludes that encouraging reading for pleasure, educational trips, the chance to go to a good nursery and school, feedback on school work and a supportive home life can help disadvantaged youngsters to get good results.
It suggests that bright, poor students should get "enrichment" vouchers, funded through the Pupil Premium - public funding for disadvantaged children - to help with educational trips, reading for pleasure and studies outside of the classroom.
Sir Peter Lampl, chairman of the Sutton Trust which commissioned the report, said: "The fact that bright disadvantaged students fall so far behind when they reach their A-levels shows that government and schools urgently need to do more to support able students from less advantaged homes.
"We must ensure that access to the best schools and opportunities for academic enrichment outside school are available to all students. It is also vital that schools advise their students on the right subject choices at GCSE and A-level so as to maximise their potential."
Professor Pam Sammons, co-author of the report, said: "There is no silver bullet that alone can make a difference but a combination of good schools and pre-schools, the right home learning environment and supportive teachers ready to monitor progress and provide good feedback can all ensure that bright but disadvantaged students get the chance of a good university education. There are important lessons here for teachers and policymakers seeking to reduce the equity gap in attainment."