Education Secretary Justine Greening wants England’s schools, including a new generation of grammars, to do more to help “ordinary working families”.
The school system needs to find ways to support those who are struggling – and not “the privileged few”, she will say in a speech later.
New government analysis shows a majority of selective school places go to more affluent families.
Recent figures showed that most child poverty is now in working families.
These “ordinary working families” are defined as not the poorest, but living on “modest incomes”, and likely to live in suburbs and coastal towns away from London.
Helping these struggling, working families, missed by other poverty measures, has become the focus of Ms Greening’s education reforms.
In a speech at St Mary’s University in Twickenham she will say “ordinary working families shouldn’t have to ‘make do,” arguing they are “the backbone of our economy, of our country”.
The education secretary will say that the school system will have to serve them better.
“Fundamentally, children need more good schools,” she will say.
There have been strong criticisms that grammar schools will exacerbate social division, but Ms Greening will defend their expansion.
“I believe that selection, in new, 21st Century state grammar schools, will add to the options available to young people, to truly help make the most of their talents.
“And grammars should not just be for one better off group in society to attend. We want to see more children from disadvantaged families get into grammars – that’s vital.”
She will say that she wants all grammar schools to change their admissions code to give priority to disadvantaged children.
Ms Greening will say “many young people from an ordinary working class background already attend our existing grammar schools”.
Although a consultation published by the government on Wednesday, examining how schools should support such “ordinary working families”, shows affluent children are currently much more likely to take places in grammar schools.
The consultation shows 36% of places are taken by children from families with below-average incomes but not receiving free meals, compared with 53% of places taken by families with above-average incomes.
In non-selective secondary schools, there are 35% of pupils from these “ordinary” families, and 32% from more affluent families, a much lower proportion than in grammars.
The analysis also says these “ordinary families” are more likely to miss out on places in outstanding schools, compared with children from better-off families.
The consultation says while there has been much attention and support for the very poorest families, there is “very limited understanding” of the experiences of children in families of “modest incomes”.
St Mary’s University, where Ms Greening is speaking, recently published research showing that counting pupils eligible for free school meals had become an unreliable measure of poverty.
The researchers said that focusing on these pupils missed families who might be working multiple jobs and living in precarious financial circumstances, but above the threshold for free meals.
The study warned that using proportions of free school meal pupils had also become an unreliable way of assessing the fairness of admissions systems.