Education Secretary Gavin Williamson laid down the rules today as he published plans for the re-opening of schools and colleges in the autumn. He said current restrictions on group sizes will be lifted to allow schools, colleges and nurseries in England to fully reopen as COVID-19 infection rates continue to fall. But schools have been told to keep children in class or year-sized "bubbles" and avoid creating "busy corridors" when all pupils return. Older pupils should be encouraged to be kept away from other groups of students and staff and a whole school, or all pupils in a year group may have to self-isolate at home if schools have two or more confirmed coronavirus cases within a fortnight. Mr Williamson said school closures "may not be necessary" if there are a number of confirmed cases if schools implement the recommended controls. But he told headteachers they will be expected to have plans in place to offer remote education to pupils who are self-isolating. The Education Secretary said:\u00a0"I know these past three months have been some of the most challenging that schools have faced. "What they have achieved to make sure that young people are kept safe and can continue to learn during this period is remarkable, and I am incredibly grateful for that. "Nothing can replace being in the classroom, so ever since schools, colleges and nurseries closed to most children, we have been working hard to ensure they can reopen as soon as possible. "We have already seen more than 1.5 million children and young people return, but we must make sure all pupils can go back to school in September, giving them the opportunity to thrive and fulfil their potential. "I want to reassure parents and families that we are doing everything we can to make sure schools, nurseries, colleges and other providers are as safe as possible for children and staff and will continue to work closely with the country\u2019s best scientific and medical experts to ensure that is the case." READ MORE:\u00a0UK schools: Gavin Williamson announces MAJOR changes for new year\u00a0 The back-to-school guidance has been developed in close consultation with the sector and medical experts from Public Health England. Deputy Chief Medical Officer, Dr Jenny Harries, said: "Thanks to the hard work of everyone, including our teachers and all school staff, there has been a decline in the rate of COVID-19 transmission in our communities. "A child\u2019s education is essential to their healthy development - we know that missing too much school can have a negative impact on children\u2019s mental and physical wellbeing. "Everybody wants children to be safe and thankfully as we have learned more about COVID-19, the evidence has shown that the risk of severe disease in children is low. "However, although the number of COVID-19 cases has declined, it is still in general circulation - so it important we ensure schools implement sensible precaution to reduce potential transmission of COVID-19 and minimise any risk to teachers and their pupils." Schools will be expected to work with families to secure full attendance from the start of the new academic year, with the reintroduction of mandatory attendance. But a headteachers' union has warned that it will be "enormously challenging" for schools to keep children apart in year-group-sized "bubbles".