This is surprising, especially after reading how many children have tested positive in the US. If they are not catching it in school, then where are they catching it? (Eg. There was the Georgia summer camp incident where there was a lot of transmission.)
Little evidence of school transmission - minister
"There is little evidence of coronavirus being transmitted in schools, Education Secretary Gavin Williamson has said.
Mr Williamson said the government was being guided by the best science as it accelerated plans to reopen schools to all pupils in England next month.
Government advisers have warned the nation may have reached the limit of what can be reopened in society safely.
But Mr Williamson suggested an upcoming study would support the government's position on reopening schools.
His comments come after
Prime Minister Boris Johnson said the reopening of schools - after months without in-person education - was the "national priority" of the government.
The prime minister, who is expected to visit a school later on Monday, is understood to have made it clear that schools should shut last in any future local lockdowns, after businesses including shops and pubs."
Continued at above link.
Here's another article with some UK numbers and info.
Could reopening schools spread coronavirus?
"Children are at extremely low risk of becoming ill from the virus.
Adults - and particularly older adults - are far more likely to be seriously ill and die from complications.
The largest study done so far, involving more than 55,000 hospital patients, found that only 0.8% were under the age of 19.
Half of all the people with confirmed coronavirus who were admitted to critical care units in England, Wales and Northern Ireland were 60 or older as of 31 July,
according to a research charity.
But more than three-quarters were over 50 and fewer than 10% were younger than 40.
Children often have "milder disease than adults", according to Prof Adilia Warris, a paediatric infectious diseases specialist at the University of Exeter, and deaths have been rare.
There have been some extremely rare cases of children developing
an inflammatory syndrome similar to Kawasaki disease, and scientists are exploring a possible delayed immune response to coronavirus.
Can children pass on coronavirus to others."
Continued at above link.
My calculations regarding the 55,000 hospital patients studied would work out as the following percentages.
50% age 60 and older
25% age 50-59
15% age 40-49
9.2% age 19-39
0.8% age under 19
)
Oh that’s a smart idea 
