It was a painstaking exercise that involved sourcing data covering more than 8,000 schools, across scores of local authorities from all nine regions in England.

And the results from the Tes investigation into the number of Covid cases in schools were not insignificant. We found that at least one in three schools have had staff or pupils test positive for Covid-19 since the start of September.

So it is perhaps telling that the first reaction of many teachers when we revealed the results on Friday was to warn that the figures that councils provided were not telling the whole story.

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Questions were raised that suggest that any underestimation of the extent of the virus in education may not just be down to local authorities. It may be because not all schools are reporting their cases in the first place.  

Unfortunately, not all schools are reporting their cases. I’ve heard from some Heads who have actually been told by PHE that they don’t need to unless they need specific advice.

- Scott Jelferson (@scottjelfs) November 13, 2020

Then there was the question of an absence of data from known coronavirus hotspots.

Coronavirus: The impact on schools

Tes asked councils to provide figures for the number of schools that have had Covid cases since the start of term.

We found that cases have been recorded in 35 per cent of schools across more than 60 areas of the country since the start of the academic year.

But many councils chose not to respond to our request for information.

And reacting to the Tes story on social media, teachers noted that among the authorities missing were some of the areas likely to have particularly high figures.

One Twitter user, MrsTG, said: “Sefton, Liverpool and Knowsley missing. One of the most affected areas in the country.”

Sefton, Liverpool and Knowsley missing. One of the most affected areas in the country.

- MrsTG (@MarieTG2) November 13, 2020

These Merseyside areas have all been hit hard by the virus, and were moved into Tier 3 - the most severe level of local restrictions - before the new national lockdown came into force.

But when asked for the number of schools hit by Covid-19 since the start of term, none provided figures.

Liverpool City Council did not respond to Tes’ request.

Sefton Council responded simply: “We are not releasing data of this kind at this time.”

And Knowsley Council did not provide figures, instead issuing a statement that suggested there were plenty of cases to report.

A spokesperson said: “We know that all of our schools want to remain fully open to all pupils but, in view of the recent increases in rates of Covid-19 in the community, we have to recognise that there will be times that this may not be possible.”

Another Twitter user asked: “Where are Lancashire and Blackburn in this list?”

Where are Lancashire and Blackburn in this list?

- Karen Casson (@KarenCasson1) November 13, 2020

Both areas were also moved to Tier 3 before the national lockdown.

When asked how many schools had been hit with Covid-19 cases, Lancashire County Council told Tes to contact the Department for Education for the information.

And Blackburn with Darwen Borough Council did not respond at all.

Then there was the Isle of Wight, which provided Tes with the lowest figures saying that just 6 per cent of its schools had been hit by the virus since the start of term.

But that prompted a tweet from Kelly Wetherick, saying: “The Isle of Wight have had more than three just in the last week.”

The Isle of Wight have had more than 3 just in the last week 🤷‍♀️

- Kelly Wetherick (@KWetherick) November 13, 2020

When contacted to clarify the figures, the Isle of Wight Council said the information it submitted to Tes at the end of last month would have been “totally accurate” but may now be outdated.

The pandemic is by its very nature a fast-moving situation. On the same day that the Tes investigation was published, the government’s scientific advisers revealed there had now been more than 1,000 clusters and outbreaks of Covid-19 in educational settings since schools fully reopened in September.

Accurate and fully comprehensive figures are hard to come by. Sadly the only thing that is completely clear is the huge pressure the coronavirus is now placing on so many of our schools.