The number of schools in England sending home groups of pupils because of Covid-19 incidents has quadrupled in a week, according to the latest official figures.
Based on attendance last Thursday, they show 4% of schools not fully open because of confirmed or suspected cases - up from 1% the previous week.
This could mean about 900 schools sending home pupils.
Overall attendance has also dipped slightly from 88% to 87%.
This means over a million children were off school that day, whether from Covid-related or other reasons, with more pupils missing from secondary schools than primary.
These are the second set of Department for Education attendance figures since schools returned in the autumn - and they show a significant increase in schools sending home groups of pupils or whole year groups because of concerns about coronavirus.
The figures, based on responses from 76% of state schools, show the situation last week, amid widespread concern about difficulties getting Covid tests for pupils and staff.
But they also show the number of schools which were fully open had increased - up from 92% to 94% - because the previous week’s figures included schools that were still carrying out a phased start to the year or holding teacher training days.
The figures show almost no state schools being completely closed - with 99.9% recorded as open.
This combination of more schools completing their reopening - and at the same time more schools sending pupils home because of Covid-19 - meant that the overall attendance figure balanced out as being similar to the previous week, from 88% to 87%.
This is well below what would be expected, with attendance rates usually around 95%.
An even lower proportion of vulnerable children, such as those with a social worker, were recorded as being at school, with an attendance rate of 81%.