It is very difficult to weigh up risk for schools, as the evidence is mixed. We do know that children seem to get it less, less severely and possibly spread it less. However there are also findings that children over 11 spread it as much as adults.
So we know that there is less risk in schools, but it is not risk free. Also, as schools have hundreds of kids, with hundreds of families attached, then the virus could seed into the community in quite a big way.
Community transmission - once it is out there - is the most difficult to trace and control.
Clusters - like in meat factories are more containable - the people work and live together usually.
Israel did become very blasé about schools, opened early and abandoned social distancing etc and they seemed to drive high community transmission. Denmark opened carefully, with children in very small units, physically distanced and also crucially I think did much of the classrooms outside to ensure ventilation.