Boris Johnson is coming under renewed pressure from Tory MPs to end school bubbles when lockdown restrictions in England are lifted later this month. Former party leader Sir Iain Duncan Smith is among 48 MPs to have signed a letter to the Prime Minister warning that the current policy is “disproportionate” and “unsustainable.” The call came after official data showed that 279,000 children in England are isolating because of possible contact with a COVID-19 case. Education Secretary Gavin Williamson has suggested that school bubbles will end when classes return after the summer holidays in September. But the letter said it is essential that schools “go back to normal” when lockdown is lifted—set for July 19—even if it is “just for the last few days of term.” “This will send an important signal ahead of the autumn that the route to freedom is a ‘one-way road’ and genuinely ‘irreversible,’” the letter …