Justine Greening insisted the government is not planning a return to an education system of "winners and losers", as she faced a grilling over the Conservatives' grammar school plans.
Theresa May is believed to be targeting a new generation of grammar schools, telling Tory MPs on Wednesday that she wanted to create a "21st-century education system" with an "element of selection".
Education secretary Ms Greening stressed today that no formal announcements had been made on potentially lifting the ban on new grammars, but she admitted the government did believe "selection could play a role".
Shadow education secretary Angela Rayner said any push for new grammar schools would demonstrate the government's "dangerous misunderstanding" of the problems facing the education system.
Ms Greening insisted that she remained "open-minded" on the issue of selection in schools as she faced an urgent question on grammars in the Commons.
But she said that "we can't rule anything out that could help us grow opportunity for all".
"There will be no return to the simplistic, binary choice of the past where schools separate children into winners and losers, successes or failures," she said.
"This government wants to focus on the future, to build on our success since 2010, and to create a truly 21st-century schools system."
Ms Greening stressed that formal announcements on the future of the education system would be made "in due course".
'New grammars will entrench inequality'
The expectation that the prime minister will lift the ban on the opening of new grammar schools has prompted widespread outcry, with the government's social mobility tsar, Alan Milburn, warning that a return to grammars could be "a social mobility disaster".
Ms Rayner echoed this sentiment as she attacked the government's position on selection in schools.
She asked Ms Greening: "Can you tell the House what evidence you have to support your belief that grammar schools will help disadvantaged children and close the attainment gap?
"At a time when our schools are facing a crisis in teacher recruitment and retention, with the thousands taught in super-sized classes and schools facing real-term cuts to their budget for the first time in nearly two decades, pushing ahead with grammar schools shows a dangerous misunderstanding of the real issues facing our schools."
Ms Rayner also warned that the introduction of new grammar schools would "entrench inequality and disadvantage". "It will be the lucky few who can afford the tuition that will get ahead and the disadvantaged that will be left behind," she said.
But Ms Greening rebuffed the criticism. "It would be wrong to discount how we can improve prospects for those children, especially the most disadvantaged, purely because of political dogma," she said. "If Labour is not willing to ask itself these difficult questions, how can it possibly come up with any of the solutions?
"We do believe selection could play a role."
Want to keep up with the latest education news and opinion? Follow TES on Twitter and like TES on Facebook