Schools closed to everyone except vulnerable children and those with a parent identified as a key worker on 20 March, in response to the pandemic.
As the lockdown measures started easing at the beginning of this month, children in nursery, reception, Year 1 and Year 6 were encouraged to return to primary schools in England, albeit in smaller class sizes.
Some Year 10 and 12 pupils – selected because they are sitting GCSEs and A-levels respectively next summer – returned to secondary schools and colleges this week.
Ministers now want all pupils in England to return to classrooms full-time in the autumn, ending a near six-month absence for many pupils.
“School is vital to every one of our children, that is why we will bring all children, in all year groups, back to school in September,” Mr Williamson said.