All schools in England should follow new government guidance and be phone-free for the entire school day, Education Secretary Bridget Phillipson has said.

In a letter to schools seen exclusively by the BBC, she said it was “not appropriate for phones to be used as calculators, or for research during lessons”, as well as during break times and lunchtime.

Ofsted will be inspecting schools on the implementation of their mobile phone policies going forward, she confirmed, with teachers also being advised not to use their phones in front of pupils.

One head teachers’ union said using Ofsted to “police” schools’ mobile phone policies was “deeply unhelpful and misguided”.

Schools were first given guidance on phones by the previous Conservative government in February 2024, but Phillipson said in her letter that it “did not deliver the clarity or consistency that schools need”.

She said the government had therefore “strengthened” the guidance issued last week, to make it “explicit” that pupils should not be using their phones at school.

Phillipson’s letter to schools comes just under a week after the announcement that the government would be launching a three-month consultation on banning social media for all under-16s in the UK.

The education secretary has encouraged teachers to “contribute your professional insight”.

Kemi Badenoch, leader of the Conservatives, has already said her party would introduce such a ban if it was in power.

Last week’s announcement also included tougher guidance for schools from Ofsted, including telling staff not to use their devices for personal reasons in front of pupils.

Recent research by the survey tool Teacher Tapp suggested 86% of primary school teachers said they were able to use their phones at school for personal use, but only during breaks, while 44% of secondary school teachers said they were allowed to use their phones freely.

Only 2% of both primary and secondary teachers surveyed said their schools banned staff from using phones entirely during the school day.

Teaching unions have generally welcomed the social media consultation, but pushed back on the suggestion of Ofsted monitoring schools’ mobile phone policies.

Paul Whiteman, general secretary of the National Association of Head Teachers, said school leaders “need support from government, not the threat of heavy-handed inspection”.

The Association of School and College Leaders also said the government had been “sluggish” in responding to the online risks posed to children.

Although the government consultation on social media concerns the whole of the UK, its guidance for schools on phones only includes England, as education is a devolved policy area.

The Senedd said last year that phones should not be banned “outright” from schools in Wales, but that schools themselves should be supported to set and implement their own policies.

In Northern Ireland, Education Minister Paul Givan previously advised schools to restrict pupils in their use of mobile phones, and has recently supported a campaign encouraging parents not to buy their children smartphones until they reach 14 years old.

And in Scotland, schools have been given government guidance on setting their own rules, such as pupils having to hand in phones before lessons, or not being allowed to use them on school trips.