https://www.bmj.com/content/372/bmj....campaign=usage
As children have mild forms of disease and teachers are able to protect themselves effectively—their rate of infection is similar to that of adults of the same age and sex2—the biggest risk associated with schools lies in transmission of the virus from children to parents and grandparents vulnerable to developing severe forms of covid-19...
The emerging consensus is that schools do not seem to be amplifiers of transmission, and that cases in schools simply reflect prevalence within the local community...
Most European countries have introduced measures220 to reduce transmission such as cohorting of pupils, physical distancing, improving ventilation of indoor settings, moving physical activities outdoors, regular cleaning of surfaces, and improving hand hygiene and respiratory etiquette. These measures also need to apply beyond the classroom, particularly transport to and from school, during pick-up and drop-off times for both children and adults, and during meal times in the school day...
The most important thing we can do to keep schools safe is to reduce transmission in the community particularly in areas of social deprivation. Reopening of schools should be phased, at a time when community transmission of the virus is controlled, and with primary school aged children prioritised for returning to the classroom to minimise both transmission within schools and the disruption caused by school closures. Although the roll-out of effective vaccines has begun, controlling transmission is even more important to keeping children in the classroom as viral variants with increased transmissibility gain hold in many countries around the world.