"Safety" of schools is safety for children, for teachers/staff, and for the community, and includes safety for those with pre-existing conditions who are at higher risk of severe Covid-19.
Fortunately, children without pre-existing conditions are at extremely low risk of severe Covid-19 disease, according to current evidence.
Now that children are back at school, our task is to maximise safety - ie the balance of benefit and risk - and minimise educational disruption from isolation and school closures.
This means reducing the occurrence of clusters in schools, and requires hard choices and ambition.
Clusters proceed in three stages. A cluster is seeded when a pupil or teacher who is presympomatic or asymptomatic brings the virus to school - hopefully the symptomatic will stay at home. The chance of this happening is greater the higher the level of virus circulating in the community. The next stage is that the school, and the school bus, acts as a potential transmission hub, the virus spreading before the first symptomatic contact is discovered.
Measures in schools and school buses to ensure hygiene, social distancing, masks, and ventilation are important to tackle this stage. The third stage is when pupils and teachers who have caught their infection at school bring it home and infect other family and community members.
Tackling the seeding of clusters by reducing the level of virus in the community is the most effective strategy to improve safety and avoid disruption, but requires hard choices. Keeping children at school may require tightening up measures in other settings, particularly indoor venues offering non-essential services. Furthermore, as individuals, we need to understand the effect of our own choices - that by disregarding social distancing measures, the addition of all those seemingly tiny extra transmission risks across many thousands of people raises community transmission and threatens our ability to keep schools open.
Policy makers need to choose a clear goal - what does "living with the virus" mean? How much virus? "Living with the virus" could mean going on as we are now, but getting better at it, with more accurate and faster diagnostics, better treatment, better public and employer observance of social distancing, masks and hygiene, better case finding and contact tracing, and better financial support for people to isolate at home.
However, "living with the virus" means lurching forward with the foot ready on the brake, a local brake for clusters, a more generalised area brake when R goes above 1. Moreover, the requirement for extensive social distancing and its economic and societal impact is constant and has no endpoint, until the much hoped for vaccine.
"Zero Covid Island", as proposed by the Independent SAGE group and Zero Covid Island group, is a more ambitious strategy.
It aims to eliminate domestic transmission of the virus entirely by a temporary imposition of the most effective measures - with fair compensation to those shouldering the burden, after which we are able to open up the society and economy to a much greater extent, while strictly controlling the importation of cases across borders. It gives the community a clear goal and endpoint. This strategy would not only allow children back to school with less disruption, but also allow those in our community with vulnerable health - both physical and mental, including children and teachers with pre-existing conditions - to participate fully again in our society and economy, as is their right.
North and South would need to work together on the island of Ireland, as they have already committed to doing with considerable success, and there would need to be travel restrictions between the countries of the UK, as is happening between the States of Australia, while elimination is attained.
There would be setbacks, as experienced in New Zealand, the "poster country" among those which have adopted this strategy, but imported outbreaks would be less frequent and smaller.
Zero Covid requires a policy decision, preparation of systems, and then a concerted push to the goal.
Teachers know better than anyone the importance of expectations in raising standards.
Zero Covid should at the very least be a policy option on the table in our quest to drive down community transmission.
Helen Dolk is Professor of Epidemiology at Ulster University.