CNN News:疫情引发美国线上教学和线下教学之争

Which of these U.S. school districts has the largest student enrollment? Miami-Dade County, Florida, Clarke County, Nevada, Broward County, Florida or Houston, Texas. According to the U.S. Census Bureau, Miami-Dade County has the largest student enrollment on this list.
At some point last year, schools in all 50 states were closed to in-person learning because of concerns about the coronavirus pandemic. Now according to edweek.org, partial closures have been ordered in five states.
In-person learning has been required in four states and the 41 other states allow in-person learning though many governments have districts decide whether they'll be open and what their restrictions are. Studies have shown that in communities were the virus isn't widespread or where masks are worn and regular testing is done, schools can be open without causing more problems.

But some researchers are concerned that where there is widespread transmission, there could be more exposure in schools and that kids and teachers who catch COVID there could spread it through their communities. There've been concerns raised by teachers about their risk of catching coronavirus.
There's a debate raging about whether virtual learning is as effective as in-person learning and experts have voiced concerns that school closures may be taking a toll on student's mental health. So there's no nationwide consensus on what the right approach is and that's a challenge being faced by other countries as well.