There’s a broad consensus that the decision on when, and how, to open schools more widely should be based on science, not an arbitrary date.

And, despite penning in 8 March as a hoped-for deadline for getting all pupils back into classrooms, prime minister Boris Johnson has promised that his plans, due to be set out on Monday, will be firmly based on the “data”.

So what data is out there, and what does it tell us about how safe it will be for children to return to schools en masse in just over two weeks’ time?

Schools reopening: What is the situation with Covid cases?

At the time of writing, the latest daily figure for people testing positive for Covid-19 in England stood at 9,236.

There were 148.8 weekly reported cases per 100,000 population in England, according to the most recent figure - a huge drop from a peak of 660 per 100,000 population on 8 January.  

Where are we heading?

Scientists from the Independent SAGE group have told Tes that, based on current trends, they expect the number of new daily UK cases to continue falling steeply over the next fortnight, from 12,718 to 4,018 by 8 March.

According to one of the group’s members, Karl Friston of University College London, the UK rate is likely to fall from the current 136.5 confirmed weekly cases per 100,000 population to around 42 per 100,000 by 8 March. They did not have separate predictions for England, but expect numbers to fall to a roughly similar, but possibly slightly higher rate.

Related: Covid rates: When did other countries reopen schools? 

Boris Johnson: We hope to reopen schools from 8 March

Read: ‘Nowhere near’ safe to open schools, says expert

But is this low enough, according to scientists?

Professor Neil Ferguson, who is part of the New and Emerging Respiratory Virus Threats Advisory Group, was last week upbeat about the prospect of lockdown easing, saying the nation is “in a better place than I might have anticipated a month ago” and we “might have some bandwidth” to open “at least primary schools” in March.

According to Independent SAGE, schools are safe to open if there are fewer than 100 new weekly Covid cases per 100,000 population.

And rates at the level projected for 8 March would fall into the “amber” category of the group’s traffic light system for school openings, meaning schools can open but assemblies must be banned and masks need to be worn.

“The numbers on the modelling are looking very optimistic,” says Friston, who highlights that Scotland and Wales are reopening to more pupils from Monday. England’s plan to open more widely from 8 March seems a “very sensible balance”, he says.

However, if the rate climbs above 50 cases per 100,000, opening schools would be classed as “high risk” by the group, meaning there should be staggered breaktimes, extra spray cleaning and no group work or PE lessons.

Other scientists question whether we are anywhere near the point of sending more pupils back into school.

Earlier this month, an expert from the government’s Scientific Advisory Group for Emergencies (SAGE) said infection levels were far too high for schools to reopen without risking another rise in Covid cases.

Professor Calum Semple told BBC Radio 4’s Today programme: “I think we need to be looking at the numbers closer to where we [were] at the end of the summer, when we really had suppressed the virus significantly, and we’re nowhere near that yet.”

On the day he voiced this concern, the rate in England was 233.7 per 100,000 people. The rate has fallen steadily since then, but we are still very far off the relatively flat numbers seen last summer, which saw daily cases fall to just 1,041 on 1 September - nearly nine times lower than the figures we are currently seeing. 

Finding out the rate per 100,000 from last summer is a little complicated as the data is less accessible before November 2020.

But Friston calculates that the weekly UK figure fell as low as seven per 100,000 on 15 July, before rising to “roughly the same levels we anticipate on March 8” by 16 September, after many schools in England had been back for two weeks.

But we are not out of the Covid woods yet. Last week, the director of UCL’s Clinical Operational Research Unit, Christina Pagel, posted a graph on social media that she said showed the “long way to go” before case rates were down to the level of last summer.

3. Cases and positivity rates also falling across all English regions & LAs. However, E. Mids, Yorks & Humber and N.East falling slowest.

Obviously falls are GOOD, BUT the green diamonds show where we were at the end of Aug last year.

There is a LONG way to go. pic.twitter.com/Wx0yx1TcaS

- Christina Pagel (@chrischirp) February 12, 2021

What about areas where rates remain stubbornly high?

Cases are not falling uniformly across the country, and areas like Middlesbrough, Corby, Sandwell, Ashfield, St Helens and Knowsley are currently seeing weekly rates that are up to three times the threshold recommended by Independent SAGE, of 100 per 100,000 confirmed cases.

Based on current trends, it looks probable that most areas will see their Covid case rates fall within that “safe” area, although some may find themselves in the “high risk” category.  

Friston predicts that, as a rule of thumb, rates are generally likely to fall by around 72 per cent between now and then, which would take Middlesbrough’s figure - the highest in England - down from 320 to 90 confirmed weekly cases per 100,000.

But he highlights that the Office for National Statistics numbers only include cases picked up through testing, which he says only account for around a seventh of the “true” number.

While this may be worrying to those schools or local authorities with cases that are close to the “unsafe” level for school openings, it doesn’t look like they will be given the option to play it safe.

The prime minister has said that he wants to take a national approach to lockdown restrictions from now on, so whatever decision is made on Monday is likely to affect the whole country.

This could be problematic, according to Friston. “There’s regional variation,” he says. “There’s current concern that in areas of the North East and North West it seems to be very difficult to get the prevalence of infection as low as in areas such as London.

“Some local authorities will have to be more cautious than other local authorities.”

Are there other considerations?

The Covid case rate is an important part of this debate, but it isn’t the only measure that needs to be looked at, and few would argue that falling numbers provide enough protection on their own.

Some scientists speaking in favour of March reopenings still advise that schools take strict precautionary measures when welcoming pupils back, including keeping classrooms ventilated, using outside space whenever possible and encouraging mask-wearing. There is also support for teachers to be prioritised for vaccines.

There is a fear that reopenings could push the “R” [Covid reproduction] rate above 1, along with hope that this could be mitigated by measures like the mass testing of schoolchildren and rapid contact tracing.

The vaccination programme has provided some confidence that we are in a better position to come out of lockdown - starting with all children returning to school. But, of course, it is always possible that the programme could suffer setbacks, or that the virus could mutate into an even more virulent form, which might force the government to rethink its “road map”.

Meanwhile, NHS leaders have been quick to point out that, while infection rates may be falling, the health system is still under tremendous pressure, and any easing of restrictions - including the return of more children to classrooms - will have to be carefully thought through and managed effectively at all levels.