More than 50 public and private schools in the Washington region and across Maryland have grappled with coronavirus outbreaks this fall, according to state and school data that provides a new look at the pandemic’s toll.

The data shows outbreaks linked to students or staff at schools in rural counties, urban areas and leafy suburbs. Sixteen people tested positive at a Christian school in Hagerstown this month, and a dozen cases were reported at a Catholic school in Southern Maryland in October.

The details come as a growing number of schools nationally are retreating from on-campus instruction. In the Maryland suburbs, Montgomery County’s public health chief urged the same shift for private schools, citing a sharp surge in coronavirus cases.

“The risk of covid-19 spreading in a school is directly related to the level of covid-19 spread in the community and safety measures in schools,” wrote Travis Gayles, Montgomery’s health officer, in a letter Thursday night to more than 200 private schools.

Gayles asked schools to consider a return to full remote instruction until the case rate — 29.3 per 100,000 residents Friday — falls below 15 per 100,000 residents. Schools should report their decisions to the county by Dec. 4, he said.

As schools began to weigh the idea — a recommendation, not an order — state data in Maryland and Virginia gave a snapshot of several weeks of school-associated covid-19 cases that health officials described as outbreaks.

Eight people at the Bullis School in suburban Potomac tested positive, according to state data this month. In Virginia, Fairfax County’s W.T. Woodson had an outbreak with five cases and Virginia Academy, a private school in Loudoun County, had one with six, according to data released Friday.

Many school leaders who responded to inquiries from The Washington Post said that they had reported the cases to local health officials and that contact tracing and quarantining were done as needed. Several said there was no sign of spread of the virus in classrooms.

At St. John’s College High School in Washington, President Jeff Mancabelli said D.C. health officials looked into 12 cases at the school after the Halloween weekend. He said because of the school’s hybrid schedules, just two students were on campus after he believes they contracted the virus. The school moved to all-virtual lessons for a period.

“We are confident these infections didn’t occur on campus,” he said.

At Bullis, Head of School Christian Sullivan said in a Nov. 9 email to families that testing at school Nov. 5 identified a student as positive.

“That student was immediately pulled out of class on Friday, classrooms were sanitized, and we worked with the family to identify contacts at Bullis,” he wrote.

Sullivan cited two other cases in that message, then reported five more in later emails to families that were obtained by The Post. In-person learning was reduced, according to the emails, which said there was no evidence of on-campus transmission.

“If we see many infections in our Bullis community, we will not be able to offer on-campus education between Thanksgiving and the winter vacation,” Sullivan wrote Nov. 17. The school did not respond to inquiries from The Post.

Many of the school outbreaks have come to light through recently created school-related outbreak “dashboards.” Maryland and Virginia have them; the District does not.

In Maryland, an outbreak is defined as at least two confirmed covid-19 cases among students, teachers or staff within a 14-day period that are “epidemiologically linked” and not household contacts. Local health officials report data to the state.

Experts called them a starting point but said they needed to expand to be helpful to parents and educators.

Leana Wen, an emergency physician and public health professor at George Washington University and former health commissioner in Baltimore, said the dashboards leave many questions unanswered, including how many total cases are linked to each school.

She also noted that without surveillance testing in schools and robust contact tracing, it is not possible to capture the extent of an outbreak. “We are not picking up on all the asymptomatic and mildly symptomatic cases,” she said.

Meagan Fitzpatrick, an infectious-disease modeler at the University of Maryland School of Medicine, said the dashboard data would be more helpful with case dates, totals by school, clarity about the number of classrooms affected and breakdowns by students and staff.

She added that while some schools may maintain there is no in-school spread of the virus, “if they are not testing in the aftermath of a case being found, then they don’t know.”

The risks have risen with soaring cases. Before the surge, schools had the benefit of lower case rates in the community, which help protect against in-school transmission, Fitzpatrick said. “When cases are high, the first level of protection is gone,” she said.

Fitzpatrick lauded the recommendation in Montgomery County to shift private school learning to all-virtual. “The risk is now three times as high as it was at the end of September,” she said, “and it’s not going down. There is no indication it’s going anywhere but up.”

The state’s largest outbreak was at Grace Academy, a private Christian school in Hagerstown, north of the Maryland suburbs, first reported on the dashboard Nov. 11.

The school did not respond to requests for comment this week, but a Nov. 9 story on ­ reported the school had cases in at least four classes and would close down in-person classes until Dec. 1, switching to remote instruction.

In the Washington suburbs, the Heights School in Potomac had four cases and St. Elizabeth Catholic School in Rockville had two cases, the data showed. The Heights did not respond to a request for comment.

A spokeswoman for the Archdiocese of Washington said St. Elizabeth had a positive case and a probable case that ended up being negative. Archbishop Neale School in Southern Maryland had 12 cases in October — half students, half staff. Five classes and their siblings quarantined for 14 days. The school transitioned to all-virtual learning for two weeks but is back to in-person instruction for families that select the option, according to the archdiocese.

Archdiocese officials said Friday they were studying the recommendation to move private schools to all-remote learning. But they underscored that schools opened with strict health and safety practices.

“These measures have proven to be successful, as we have not experienced a surge of cases and have successfully partnered with local health officials to manage the few cases that have arisen,” the archdiocese said in a statement.

Maryland data showed St. Andrew’s Episcopal School, which President Trump’s son Barron attends, had two positive cases. The school declined to comment, but a Nov. 4 letter it sent to families said the cases involved contract employees, not students or staff.

Maryland’s largest teachers union called the dashboard inadequate. “Having something up there is helpful, but it does not have useful information,” said Cheryl Bost, president of the Maryland State Education Association.

Some people hear about a case at a school and see nothing posted, she said. “It leaves a lack of trust,” she said. “Are people really taking it seriously and reporting it . . . or are they hiding it?”

Asked about expanding the dashboard, Maryland health officials said they are continuously evaluating data and reporting systems and would update them as more information is available.

With much about schools in flux, the District’s traditional public school system started to bring some students back Wednesday to use classrooms for remote learning. Some charter schools have been operating in the city since September. Amid rising cases in the region, Rocketship Public Charter School announced this week that it was halting in-person learning, although it did not report any cases at its campuses.

Perry Stein and Hannah Natanson contributed to this report.