A teaching union leader has questioned whether scientific evidence supports education secretary Gavin Williamson’s claim that schools are not driving transmission of Covid-19.

The education secretary has said that “scientific evidence does not suggest that schools and colleges themselves are driving virus transmission” in a letter sent to headteachers over the weekend.

Mr Williamson has written to heads following the controversy over the government’s last-minute announcement that it was asking secondary schools and colleges to administer 11 million Covid tests to students from the start of next term.

Coronavirus: Are schools increasing infection?

The education secretary wrote to assure school leaders that running these tests was not mandatory.

However, his letter has prompted questions from a union and school leaders over claims that schools are not responsible for driving transmission of the coronavirus.

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Kevin Courtney, joint general secretary of the NEU teaching union, has challenged the Department for Education to produce evidence to support this claim.

When Tes asked this question, the DfE responded by citing the findings of the recent School Infection Survey study, which it says relays points about school and community infection.

Mr Courtney said: “If Gavin Willamson’s comments are based on the recent School Infection Survey study, we do not think that the research supports that conclusion.

“Its findings that the levels of schoolchildren and teachers with coronavirus mirrors the proportion in the local community is not the same thing as saying that schools do not drive transmission.  

“And as that study makes clear that in the first round of testing they did they only tested pupils who were in school.

“This means those pupils with Covid-19 symptoms and those instructed to self-isolate were not tested so you cannot make comparisons between school and the wider population from it as some of the pupils who may have had Covid would not have been included.

“Mr Williamson’s claim is certainly not supported by the big increases we have seen in both primary and secondary of Covid infection rates among pupils and it is not supported by the comments of Matt Hancock when the health secretary announced urgent plans for mass testing of secondary school pupils in London, Essex and Kent because of particular concerns about Covid rates in that age group.”

Mr Williamson’s claim that schools are not driving transmission of the virus has also been questioned by a headteacher who argues that the government’s communication to schools on the issue is incoherent.

In the letter, the education secretary goes on to say that the government’s plans for mass testing “should reduce risks of transmission both within settings [schools and colleges] and within the community.”

And he says that “infection rates remain higher than we would like amongst secondary-age students”.

The letter also says that mass testing is not needed in primary schools because the transmission rates there are significantly lower.

The headteacher, who has asked to remain anonymous, said: “This letter is another confused and incoherent communication from a department that has lost all credibility with school leaders and governors.

“In it we are told that schools are not driving transmission of the virus but then later in the same email we are told that this mass testing plan is needed to drive infections in schools down. It is just more confusion and more contradiction.”

The letter sent to headteachers on Saturday is the education secretary’s response to the controversy surrounding the government’s Covid testing plans for school students.

It comes after a joint warning by education unions and organisations that the government’s plan for mass testing in its current form is “inoperable” for most schools and colleges to carry out “in a safe and effective manner”.

Last week the School Infection Survey study concluded that school outbreaks of Covid-19 may be because the virus is being taken into each school several times rather than transmission between pupils.

Early findings from the study suggest that the proportion of schoolchildren and teachers with the coronavirus mirrors the proportion in the local community.

Dr Shamez Ladhani, a Public Health England consultant epidemiologist and chief investigator on the survey, said: “We know that there is infection happening in school-age children. What we don’t know is the dynamics of that infection - whether it is occurring in school or outside schools or at home.”