A hearing into the science behind the opening and closing of schools during the pandemic took place today at a meeting of the Commons Education Select Committee.
Top Department for Education scientific advisers and the government's deputy chief medical officer took MPs' questions.
Here are seven things we learned from today's session.
1. The DfE fears that Covid testing of close contacts in schools could increase virus transmission
The Department for Education's programme of keeping close contacts of Covid cases in school if they test negative carries "a potential risk" of increasing transmission of the virus, according to a senior adviser.
Dougal Hargreaves, the DfE's deputy chief scientific adviser, told MPs today that the aim of using rapid lateral flow tests for daily checks on contacts of confirmed cases of Covid-19 was to improve attendance in schools.
He told the hearing there was a "strong feeling" that Covid cases were resulting in too many pupils being off school last term.
2. The DfE ordered London schools to stay open before Matt Hancock revealed fresh Covid concerns
There has been controversy over education secretary Gavin Williamson's claim that the "none of us knew" about the new variant of Covid when the DfE took legal action to keep schools in Greenwich open at the end of last term.
This claim has been questioned because health secretary Matt Hancock had already told Parliament about the new variant earlier the same day – before the DfE issued a legal direction on the council ordering it to back down over plans to ask schools to move to online learning in the final week of term.
However, the DfE's chief scientific adviser, Osama Rahman, told MPs today that the letter to Greenwich Council had been written before Mr Hancock made his statement – even though it was issued to the council afterwards.
3. Schools returning after February half-term is not a 'fixed date'
When asked whether schools will reopen after half-term, Jenny Harries, the deputy chief medical officer for England, said: “It is a Department for Education policy date, but it seems a perfectly reasonable assumption in the sense of if you’re looking at the epidemiology, you’re watching a wave of virus come across the country.
“We can see it’s hopefully starting to level off now in the original areas where the new variant rose and we have a national lockdown and we can start to see that those numbers are starting to be contained."
However, she added: “What I can’t guarantee – that is, in this interval between now and February – [is] that there wouldn’t be another variant, or we may find some other epidemiological change.
“So I think these are very sensible time estimates but they need to be understood as not fixed dates, and that would apply to anything in any department in relation to the pandemic.”
4. Schools may open more widely on a regional basis
Dr Harries also said that schools could open more widely on a regional basis, telling the committee: “I think it’s likely that we will have some sort of regional separation of interventions.”
She said there would likely be a "differential application" of when schools could open to all students based on the different transmission rates across the country – for example, schools might be able to open earlier in London.
But she added that schools will be at the top of the priority list to ensure that the balance of education and wellbeing is “right at the forefront” of consideration.
5. Staff vaccinations won't help schools to reopen, the deputy CMO believes
Dr Harries also told the committee that vaccinating teachers and school staff would not help schools to open sooner.
She said immunisation from Covid-19 for staff was not the “limiting factor” for opening schools to more students – rather, "community transmission rates” were.
She continued: “Once we start to see that decline, we’ll be stepping back probably to some sort of tier system or approach, and schools will reopen.
“They weren’t shut because there was a specific risk in that setting, and while I recognise teachers will be concerned, of course, that concern is shared right across a number of our key workers.”
6. There's uncertainty over schools' role in transmission
Professor Russell Viner, president of the Royal College of Paediatrics and Child Health, said there was "uncertainty" over the roles schools played in rates of transmission.
"We remain in a situation of really quite a lot of uncertainty about the roles of schools in transmission," he told MPs.
"And I think one of the things that’s important is to separate out school-aged children from schools. And without making too fine a point of that, clearly children and young people spend a lot of their time in schools, but it is by no means all of their time."
He said younger children played a "relatively minor" role in transmission, adding that "what we saw particularly from November was high rates of viral prevalence and the frequency of the virus particularly amongst teenagers".
Professor Viner said there was a complex interaction of the biology – how likely a child or young person is to transmit – with social mixing.
He said children under 12 were less susceptible to catch or transmit the virus, and children and young people were less likely to be symptomatic, which also reduced transmission.
"But what children and particularly teenagers do is socialise or socially mix a lot more than most adults," Professor Viner added.
There was a balance between a high level of social mixing outside school and biology, with social mixing more responsible for high transmission rates, he said.
"We know that schools are quite contained places – they are a place, of course, where you bring a lot of young people together but they are also places where their behaviour is contained and is containable, and there’s quite a lot of evidence that with good mitigations in place that transmission can be reduced."
7. Children have experienced 'mental health harms'
Professor Viner also told MPs that children have experienced “considerable mental health harms” during the pandemic.
He added that paediatricians and child and adolescent psychiatrists are saying there is “more pressure on eating disorder services” amid Covid-19.
Professor Viner said: “The most important thing we can do for our children and young people’s mental health is to get schools open again and get face-to-face learning and peer interaction happening.”