RALEIGH, N.C. — North Carolina health officials are reporting 170 ongoing COVID-19 clusters in K-12 schools or child care settings.

The state health department says school districts that don’t require masks are seeing substantially more spread of the virus and hours of lost learning.

Union County Public Schools, the state’s sixth largest district, had about one in eight of its more than 41,000 students under quarantine as of Friday, after the district voted down a mask requirement last month. The more than 5,200 students were placed under quarantine after 337 pupils tested positive for the virus last week.

Meanwhile, the Wake County Public School System, where masks are mandatory and which is four times larger than Union County Public Schools, has less than a fourth the number of students quarantined. Data from the Wake County district shows less than 1,300 of its more than 161,000 pupils were quarantined last week.

The weekly report state health officials updated on Tuesday shows the Union Academy Charter School in Monroe has the worst cluster in North Carolina, with 111 cases, including 98 among children. About one in 20 of the charter school’s students were infected. Charter Day School in Brunswick County has the next highest cluster of 81 infected children.