Secondary schools and colleges in Wales will close to almost all students next week and lessons will move online in an effort to stem the growing spread of coronavirus, the Welsh government has announced. The Welsh education minister, Kirsty Williams, said the public health situation in Wales was deteriorating and she had been advised by the chief medical officer that learning should be moved online for secondary school pupils as soon as possible. This contrasts with England, where the health secretary, Matt Hancock, has announced that mass testing will be rolled out in secondary schools in seven boroughs of London with the highest Covid rates, as well as in Kent and Essex, to try to stem the rapid spread of the virus. The Welsh decision will fuel demands by teaching unions and parents to move learning online in English schools in the final week of term. Many in areas of high infection are already struggling to remain open, with staff off sick and large numbers of pupils self-isolating. Many parents are threatening to keep their children at home. There have been no cases of Covid in almost half of all Welsh schools since September, but Williams said the decision to move online had been made because education settings staying open could contribute to wider social mixing outside. Despite the recent firebreak, rates of Covid-19 in Wales have exceeded 370 per 100,000 people, and 17% of all those taking a test are getting a positive result. The reproduction number – the R value – in Wales has increased to 1.27. “Every day we are seeing more and more people admitted to hospital with coronavirus symptoms,” Williams said. “The virus is putting our health service under significant and sustained pressure and it is important we all make a contribution to reduce its transmission. “I can therefore confirm that a move to online learning should be implemented for secondary school pupils and college students from Monday next week.” Vulnerable pupils may be allowed some “in-person” teaching, and primary and special schools will be encouraged to stay open, because of the challenges of self-directed learning among those children. The decision taken in Wales comes days after schools in England were told they could take an additional inset day on the last Friday of term to allow staff “a proper break” from identifying potential Covid-19 cases before Christmas. The announcement was greeted with derision by many school leaders. Paul Whiteman, the general secretary of the National Association of Head Teachers, questioned why schools in England were remaining open. “This is clearly a very serious new development, and the government’s first priority must be the safety of those involved,” he said. “The government is yet to explain why during this emergency testing period public health is best served by schools remaining fully open. A very short-term period of home learning while test results are obtained would ensure further transmission does not occur in schools amongst the most affected group.” Kevin Courtney, a joint general secretary of the National Education Union, welcomed plans for mass testing but said it should be rolled out to more areas where infection rates remain high. “The decision to move all secondary teaching online in Wales is a much more robust response to an increasingly worrying situation,” he said. The government in Westminster remained adamant that schools in England should stay open. Following the Welsh decision, a Department for Education spokesperson said: “Keeping schools open remains a national priority because, as the chief medical officer has consistently said, not being in school damages children’s learning, development and mental health. “The right approach to reducing the number of cases is following the protective measures in place, including secondary students wearing face coverings when travelling to and from school and in communal areas, and accessing testing where appropriate.”