Around one in 20 children in England are out of school because of issues linked to the pandemic and lockdown, according to the the Children's Commissioner.
There are about eight million pupils who go to school in England so one on 20 is about 400,000 children.
But Anne Longfield, the Children's Commissioner whose job it is to look after the rights and welfare of children, pointed out that the number of pupils sent home due to an actual positive Covid-19 case was very small.
As many children are in bubbles at school, one child testing positive can led to hundreds of children having to self-isolate at home as a precaution.
She said: "A lot of the children that aren't in school don't have symptoms themselves, but are in year groups with children who might."
She added it was important for the government to get Covid tests to schools quickly.
Quoting official figures, she explained that one in 20 children, or 5%, are normally away from the classroom anyway - but an extra 5% of children are out of the classroom at the moment.
Ms Longfield told the BBC that the number of children back in school was good, thanks to the heroic efforts of teachers and school staff, and said the number of schools forced to close due to an outbreak, or having to send pupils or class groups home, was still very small.
Testing for the coronavirus is becoming harder as there are more people being tested and tests are becoming harder to access.
A survey and comments by the The National Association of Head Teachers suggested schools were having a really hard time with tests.
Paul Whiteman, the head of the Teachers group NATH said: "Tests for Covid-19 need to be readily available for everyone so that pupils and staff who get negative results can get back into school quickly. But chaos is being caused by the inability of staff and families to successfully get tested when they display symptoms.
"This means schools are struggling with staffing, have children missing school, and ultimately that children's education is being needlessly disrupted."
Suspected Covid cases are expected to rise in the winter months when the usual common colds. coughs and flu kick in.
Anne Longfield spoke of how difficult it will become for teachers, parents and pupils to tell the difference between the common illnesses and coronavirus, if the testing situation doesn't improve.
"A lot of problems come because teachers are showing symptoms and therefore need to be tested and this affects the schools, especially small ones, because there comes a point when you can't run a school because there aren't enough staff."
Has anyone in your school been sent home with symptoms? Has your bubble had to isolate, let us know in the comments below.