The government has said it will introduce a legal ban on smartphones in schools in England.
Education minister Baroness Jacqui Smith told the House of Lords on Monday that the government would table an amendment to its landmark Children's Wellbeing and Schools Bill "creating a clear legal requirement for schools" on the matter.
The Department for Education (DfE) said the move would give "legal force to what schools are already doing in practice".
Education Secretary Bridget Phillipson had written to schools earlier this year encouraging them to follow new guidance that schools be phone-free for the entire day.
The government has said it will put that guidance on a statutory footing, which means schools must pay attention to it.
It argues that this is different from what the Conservatives have been advocating, which is an outright legal ban.
Conservative shadow education secretary Laura Trott said the amendment, which is due to be tabled in the coming days, was "fantastic news for headteachers, parents and pupils across the country".
"For over a year, Labour dismissed this as an unnecessary gimmick, and just last week the education minister claimed the problem had already been solved," she wrote on X.
"I'm glad they've now listened, this is the right step for improving behaviour and raising attainment in our classrooms."
For the government, Baroness Smith told the House of Lords they had taken "not seen, not heard" - meaning phones must be off and in a bag - out of the guidance as an option for schools and were willing to consider "whether we should be stronger on that".
Some schools have chosen to have lockers or magnetically sealed pouches for phones.
The details of the government's amendment have not yet been published.
The Liberal Democrats said ministers must now "ensure all schools have the necessary support and funding to manage this transition".
The party's schools spokesperson Caroline Voaden said they had "delivered a major win for pupils, teachers, and families" by "dragging the government" towards introducing a ban.
For Reform UK, education spokesperson Suella Braverman said phones were "fuelling distraction and undermining discipline" in schools.
She said the existing guidance did not go far enough, and that a "clear, enforceable ban to protect children is the right thing to do".
A Green Party spokesperson said they were "deeply concerned" about the potential harms caused by phones, adding that a "thorough consultation process" would be key to creating "effective solutions" for schools.
The DfE said it had been "consistently clear that mobile phones have no place in schools" and that the majority already prohibit them.
A spokesperson said the amendment "builds on the steps we've already taken to strengthen enforcement".
Schools' mobile phone policies will be monitored as part of Ofsted inspections from April, they added.
"We will always put children's interests first, including through this Bill – which is widely recognised as the biggest piece of child safeguarding legislation in decades."
The Bill had been stuck between the House of Commons and the Lords, after the latter house voted in favour of a Conservative amendment calling for phones to be banned in February.
Earlier this week, the House of Lords accepted shadow education minister Baroness Barran's suggestion that the bill should provide potential exemptions to sixth form students, students in boarding schools, and for those using phones as medical devices.
The head of the Association of School and College Leaders said the legal backing for the guidance "doesn't really change very much" because most schools already enforce their own bans.
"What would really be helpful is for the government to make funding available to schools for the safe and secure storage of mobile phones, such as storage lockers or locked pouches," said the union's general secretary Pepe Di'Iasio.
He also called for "much tougher regulatory action taken to tackle the harm caused by social media and the excessive use of smartphones," which generally happens outside of school time.
Because education is devolved, the approach to phones in schools varies across the UK.
The Scottish government brought in guidance allowing headteachers to implement phone bans in schools in 2024.
In Wales, there is no national ban but heads have the power to ban or restrict the use of devices in their own schools.
And in Northern Ireland, a phone-free pilot scheme in nine schools has just ended, with a report due to be published in June.
Additional reporting by Branwen Jeffreys and Kate McGough
