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 attendance statistics.
The figures, based on Thursday of last week, show 4% of schools not fully open because of confirmed or suspected cases - up from 1% the previous week.
This could mean about a thousand schools sending home pupils.
Overall attendance has also dipped slightly from 88% to 87%.
These are the second set of weekly 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 getting Covid tests for pupils and staff.
But they also show that 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.
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%.
But it means about one in eight pupils were not in school that day - well below what would usually be expected, with attendance rates usually around 95%.