If we can only have 6 people in our houses, how can we have 30 children in a classroom? It’s a reasonable question. But it’s not a contradiction; in fact, these measures are connected and coherent. The following explanation is a simplification, but illustrates the principle. 1/8

The virus spreads by finding ways to transmit from the very small number of people who have it (fewer than 1 in 2000 right now) to all those who are susceptible to it. What matters is the total number of contacts at a population level. 2/8

We have about 5 million people in the country. If each of us had, as we would have this time last year, say 10 close contacts per day, that’s 25 million opportunities per day for the virus to transmit. (5 million x 10 contacts / 2 to remove duplicates. 3/8

About one million of the population are of school-going age. If the other 4 million reduce their close contacts to, say, just 2 per day, we are down to 9 million close contacts per day. We have reduced the opportunities for the virus to transmit by more than 60%. 4/8

If we also reduce the risk that our close contacts might lead to transmission (physical distancing, hand/respiratory hygiene face coverings where appropriate) even if these measures only reduce the risk by half then we have reduced the risk of transmission by about 80%. 5/8

If the basic reproduction number of the virus is between 3 and 5, then this 80% reduction in transmission will be enough to bring R below 1, and the number of infections will decline. 6/8

Simply put, if older adults starve the virus of opportunities to transmit (limiting our contacts and being careful) the young can have the higher numbers of contacts that classroom education requires; the sum total of all contacts for the population level remains low. 7/8

The risk is even lower if (i) the level of disease in the community is minimised (ii) appropriate precautions are taken in schools. We can all contribute to the first, and teachers and principals have done extraordinary work to make schools as safe as possible. 8/8

My thanks to @CHeDS_ie and @gleesonj for their assistance in thinking this through, and the wider IEMAG group for their support.