Here in Belgium kindergarten and primary schools were reopened in June for about 3 weeks until summer holiday started. The kids didn't have to wear masks, nor the teachers while in front of their class. Teaching was more or less like before, albeit with a bit more distancing between teacher and kids.

Outside the classroom the kids from one class were not allowed to mix with kids from another. The playground was divided up in several areas and each class was assigned one. Breaks were in two shifts and all toys were washed in between (and rotated between areas). Dropping off and picking up the kids was also in two shifts and spread over as much entrances as possible to reduce contact with other bubbles. No parents allowed on the school premises.

As far as could be judged from those few weeks this didn't seem to impact the infection numbers. Even better was that the kids could have a more or less normal ending of the school year. If nothing changes my guess is that in September schools will start again in the same modus operandi, which I'm okay with.

But high school and up, that's a different matter...