Professor Calum Semple, a member of Sage told BBC Breakast: “The subtle question about transmission and teachers, and bringing it home, well the school infection survey is showing that primary school children are half as likely to have had it and probably half as likely to transmit it.
“Secondary school children (are) slightly less protected because as they become adolescents they effectively have the biology of an adult, but even there, they’re half to a quarter as likely to have had it and transmit it.
“So the main driver is not the pupil-teacher relationship.
“When we talk about schools, it is the fact that the school brings adults together, whether that’s teaching staff, the domestic staff, the catering staff, and it’s an opportunity for mixing.”
He said the issue was down to “the fact that schools are a place of work”.
Prof Semple said it was “inevitable that we will see a rise in cases” as schools go back, but added that it was not so important if the reproduction number (the R) rose slightly.
He said it was more about “the absolute number of cases going to hospital and needing intensive care”.
The advice for teachers “is going to be wearing face masks, being really careful in the common room – their colleagues are more of a risk to them than the children.
In Scotland, Primary 1 to 3 pupils returned to the classroom a number of weeks ago, while P4 to 7 pupils are due to return on March 15.
There will be a phased return for secondary school children on the same date, but Nicola Sturgeon has said there is a “clear expectation” all secondary school pupils will return full-time after the Easter holidays.
In England, millions of children in England are returning to school on Monday after more than two months studying at home during lockdown.
Many secondary schools will have a phased return during the week, allowing pupils to take Covid tests, and face masks will be worn in classrooms.
Most primary schools are expected to open for all pupils from Monday.