Poorer families could be paying premiums of hundreds of pounds for online learning after the government failed to make any school-age sites exempt from mobile data charges, Tes can reveal.
Three months ago, the Department for Education said telecoms companies would wipe costs for "selected educational resources" to help disadvantaged pupils get online during the Covid-19 crisis.
But asked which sites have been made free to access, the DfE admitted that only Hungry Little Minds – a resource for 0 to 5-year-olds – and Edenred, which is used to order free school meals vouchers, are currently "zero-rated".
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This means data charges still apply to all of the DfE's recommended online educational resources, as well as the government-funded Oak National Academy.
Tes has established that this could come at a huge cost to families without broadband – as using 4G data to visit Oak's site alone could set them back up to £860 per month*.
Coronavirus: Families facing big internet bills for remote learning
Matt Hood, Oak National Academy's principal, has said it "can't be OK that we charge children from low-income families more to get educated at home than we do wealthier ones".
He warned that poorer families often have to pay a premium for online education because they do not have access to broadband, while speaking at a Teach First webinar on digital access last week.
"If you're a poor family in England, you pay more for your gas than you do if you're a rich family, because you're on a meter and it costs more," he said. "If you're a poor family in England you pay more for your electricity for the same reason.
"Currently, if you're a poor family in England, you pay more to educate your children, because you're more likely to get that through a mobile phone provider than you are free broadband. And that's a real problem and needs national solutions reasonably urgently."
Research carried out earlier this year for Digital Access for All, a taskforce set up by the Learning Foundation, found that at least 100,000 households with school-aged children had no broadband connection.
In April the DfE announced a "new major package to support online learning" that included the pledge that "the country’s major telecommunications providers will make it easier for families to access selected educational resources by temporarily exempting these sites from data charges".
However, it has failed to achieve this for any school-age sites.
Anne Longfield, the children's commissioner for England, told Tes it was a "real missed opportunity".
"The coronavirus crisis has highlighted the digital divide that exists for many families," she said.
"This was a positive and welcome innovation by the government and I’m disappointed to learn that it hasn't been expanded to cover more educational resources.
"This seems like a real missed opportunity and I hope that the government will work urgently with telecommunications providers to expand it over the summer."
Mary Bousted, joint general secretary of the NEU teaching union, said the department's failure to make more sites zero-rated was symptomatic of a "government disease", whereby promises are made but not kept.
"I think that falls into what is becoming a government tradition of big announcements which are not then followed through," she said.
"And it brings government into disrepute when it continues repeatedly to make a big announcement but not then back it up with concrete action, which results in what has been promised being delivered.
"And I'm afraid that is just another example of what is a bit of a government disease at the moment."
James Turner, chief executive officer of the Sutton Trust social mobility charity, added: "We support the government’s steps to introduce a temporary data charge exemption on sites which provide vital education for children, but at the moment it doesn’t go far enough.
"We'd like to see a greater number of sites, including the Oak National Academy, free of data charges, so that the most disadvantaged children in our country can access the same resources as their peers."
The DfE said it was working to improve internet access in a number of other ways, including by providing pupils with "free additional data" and "free access to BT wi-fi hotspots".
The department also pointed to the fact that it has sent nearly 50,000 4G routers with a free data allowance to vulnerable and disadvantaged pupils.
However, the DfE's own statistics show that the first of these routers were not dispatched until 18 May, nearly two months after schools closed to the majority of pupils.
And 50,000 routers would cater for at most half of the minimum 100,000 households in the UK with no broadband access.
A DfE spokesperson said: "We recognise the importance of internet access, which is why we have now provided almost 50,000 free personal 4G hotspots to disadvantaged families that need them.
"The department is working in partnership with BT to offer free access to BT wi-fi hotspots for certain disadvantaged pupils and we are working with the major telecommunications companies to provide access to free additional data to families who rely on a mobile internet connection while the coronavirus requires pupils to learn from home.
"Schools have gone to great lengths to provide both online and offline provision; with organisations such as the BBC producing additional educational content accessed via the TV and many hard-copy resources offered by a range of high-quality publishers.
"This government has put in place a host of measures to support remote education, and is investing in ensuring that all children are able to catch up as they return to school."
In regard to Tes' estimate for the cost of using 4G to access Oak's lessons, the DfE said: "These figures are completely hypothetical."
*Based on Vodafone's standard "pay as you go" plan, using 405MB of data per day over the course of July's 23 working days would cost roughly £860. If a pupil accessing Oak purely through their 4G connection completed three lessons per day, for each working day in July, Tes estimates they would burn through 405MB of data per day, or 9.3GB per month. This is based on one lesson for pupils in Reception to Year 10 averaging 135MB.