There is a "strikingly large" gap between how well pupils from disadvantaged backgrounds do, compared to those from wealthy families.
Research by the Institute of Education revealed that on average, children whose parents work in management or professional careers are eight months ahead academically than youngsters whose parents are unemployed.
"The finding that social class is still such a strong predictor of differences in the cognitive and educational scores of five and seven-year-olds confounds a good deal of received wisdom," said Dr Alice Sullivan, principal author of the study. "For example, Nick Clegg, the deputy prime minister, recently blamed low levels of social mobility on class-based differences in parenting."
She suggested that the government may achieve more with redistributive economic policies than through parenting schemes.
The coalition government announced plans to introduce a pupil premium earlier this year, giving additional money to schools with high numbers of disadvantaged students.
Education secretary Michael Gove has allocated around £2.5 billion for this.
Posted by Tim Colman