Labour members have voted to effectively campaign for the abolition of private schools at the next general election.
In a vote at the Labour Party Conference in Brighton, delegates backed a motion which calls on the next manifesto to commit to "integrate all private schools into the state sector".
It means the withdrawal of charitable status and "all other public subsidies and tax privileges", including business rate exemption, from private schools.
The motion adds universities would have to admit the same proportion of private school students as in the wider population, currently 7%.
Endowments, investments and properties held by private schools would be "redistributed democratically and fairly" across the country's educational institutions, it added.
The vote in favour of the motion came after shadow education secretary Angela Rayner said a future Labour government would scrap the "tax loopholes" which benefit private schools, in its first budget.
At the party conference it was also announced that Labour would move to scrap schools inspectorate Ofsted if it was in government.
Jeremy Corbyn said the Ofsted process created “absolutely enormous” levels of stress for staff and pupils.
Addressing the conference in Brighton, Ms Rayner said she will task the Social Mobility Commission - which the party would rename the Social Justice Commission - with "integrating private schools".
She added: "We will set that commission to making the whole education system fairer through the integration of private schools.
"Myself and John McDonnell will set out further steps the Labour government will take, but I can say today that our very first budget will immediately close the tax loopholes used by elite private schools and use that money to improve the lives of all children."
The motion on private schools, moved by Battersea Constituency Labour Party, said conference believes Labour "must go further" than the 2017 manifesto to challenge the "elite privilege" of private schools who "dominate the top professions".
It added: "The ongoing existence of private schools is incompatible with Labour's pledge to promote social justice, not social mobility in education."
Holly Rigby, a spokesman for Abolish Eton, said: "This huge leap forward is a testament to the hard work of grassroots Labour members and the ambition and determination of Angela Rayner and John McDonnell."
She added: "We will dismantle systems of privilege and inequality and build a society that works for the millions and not the millionaires."