In regard to reopening US schools, one country presents a cautionary tale: Israel. After opening schools to smaller “capsules” of students in early May, Israel removed class size restrictions May 17 and most kids were back in person in full size classes.
wsj.com/articles/israe…
wsj.com/articles/israe…
Two weeks after that, cases began to increase in Israel, with notable outbreaks in schools (particularly middle- and high-schools). By last week there were 1,335 cases among students and 691 among staff.
Schools have been identified by the health department as being common sources of infection. These outbreaks have been disruptive, with 125 schools and 258 kindergartens being closed again since classes were restarted in May.
Also, Israel had policy of quarantining those who work at or attend the school is a case was found there, which has led to the two week quarantine of “more than 28,000 students and educators.”
Many believe the school outbreaks seeded community outbreaks, including Israel's Health Ministry. Cases in the country grew from 50/day in early May on average to 1,500/day more recently. 
Israel relaxed a number of restrictions concurrently with the reopening of schools there, so there are disagreements about causality here – was community transmission driving school outbreaks or vice versa.
In addition, the country’s generally lax efforts to implement social distancing, hygiene, and prevention in schools is thought to have contributed to outbreaks. In contrast, many European and Asian countries that have opened schools have been more cautious in this regard.
At the very least, the Israel experience shows schools can be venues for outbreaks particularly in the context of ongoing, broader community transmission of the virus.
So would US reopenings be closer to that of European & Asian countries – with low levels of community transmission and stricter protocols – or more like Israel whose schools opened at the same time as there was community transmission with lax protocols?
For its part, Israel readjusted its policies for fall reopening: students in kindergarten to fourth grade will return as normal but middle- and high-school students will have a both in-person and distance learning.
