Regarding schools in Portugal there is discussion about implementing a mixed system. Some classes can be taught remotely, so that students stay at home at least a few days every week. Also, to avoid crowding public transports, there is talk of offsetting school schedules and work schedules.
My kids are in University, and from mid-March to mid-July they had remote classes and exams. Wasit ideal? No. But it can work.
Pre-primary schools (up tp 5 years old) have reopened in 1st June, so far I only heard about 1 or 2 outbreaks, promptly taken care of.