The Royal Society commissioned a report (the DELVE Initiative) called "Balancing the Risks of Pupil Return to Schools", which brought together many experts from different specialisms and considered the experience of other countries.
It was published on 24 July and the government claims to have studied its findings.
This is what it has to say about face masks in schools:
"The use of face coverings or face shields has not been recommended in the Government’s guidance for schools unless children or staff display symptoms of COVID-19 and if “direct personal care” must be administered on school grounds.
Although its use in younger children may not be practical or effective – emerging evidence suggests that there may be less viral transmission from children to adults and that the dominant mechanism in young children may not be from breathing, coughing or sneezing (see section 3b) - its use should be considered for all adults (teachers, non-teaching staff and parents at school) and older children in schools, especially if there is a high rate of viral transmission locally and physical distancing is not possible. In line with the Government’s guidance, this should include its use if public or school transport is used to travel to school.
The DELVE report on masks published in May recommends the use of face masks or face coverings to reduce onward transmission where physical distancing is not possible, especially in crowded places. This is based on the emerging scientific evidence that shows a decrease in the rate of coronavirus infections where mask-use is compulsory and its usefulness in limiting how far breath can travel. This advice should not be ruled out for schools.
Although not all countries in our international review appeared to make use of masks or face coverings in their schools, those with a relatively high number of COVID-19 cases recommended its use in areas where distancing is not possible or where mixing outside of class groups occurred, e.g. in some classrooms, hallways and on transport, in for example France, Switzerland and in Israel. More recently, in the US, the American Academy of Pediatrics and the Centers for Disease Control (CDC) have recommended the tailored use of masks and face coverings when schools open at full capacity in Autumn. The CDC has advised schools to teach and reinforce the use of cloth face coverings for staff and children –again, older children in particular – except those under the age of two years, those who are unable to remove the mask without assistance and those with breathing challenges.
There is some concern that the use of masks will impede learning. Research has previously shown that the observation of the face, including the mouth is an important tool for learning and language development. While this is important for young children, the use of face coverings will likely provide greater benefit at less risk to language development for older children in secondary schools.
(my bold)
The conclusion is to recommend face masks for all in secondary schools, but not primary schools.
