School reopening has become a tangled logistical process worldwide, as public officials, administrators, teachers, parents and students have had to debate measures like face shields, ventilation, shift learning and whether to go virtual partially, or altogether. Most large school districts in the country, with the exception of New York City, have gone all virtual for most or all of the fall semester, because of stubbornly high virus rates and concerns from educators, their unions, and some parents.
Reopening has become particularly fraught in New York, where Mr. de Blasio has twice delayed the start of in-person classes because of a staffing crisis and pushback from the unions representing city teachers and principals.
School systems around the world have seen widely diverging outcomes when they reopen. Some countries, like Israel, have seen explosive outbreaks, despite containment measures. Others, like Ireland and South Korea, have kept schools open without major problems.