The 74

When kindergarten teacher Tabitha Brown received her class list for this fall, there were 27 names on it. But then her school, Global Village Academy, a charter north of Denver, announced it would start the year virtually. The list dropped to 18.

Six weeks later, enrollment inched upward as the school reopened, only to fall again in a month when it closed due to rising COVID-19 cases. Brown’s class is just one example of the disruption affecting classrooms as students fall off the radar...