At precisely 9 a.m., high school history teacher Gabriel Elias went live at his dining room table.

“Good morning, good morning, everybody!” Elias said, flinging his arms wide and nodding toward his laptop camera. Muted laughter rose from a nearby room, and his wife quieted the couple’s 4- and 9-year-old children.

Elias gave a special greeting to one student named Fatima, who had ordered him to make the broadcast “interesting.”

“I’m new to this,” Elias said, “but I’m going to try.”

It was the second day of the coronavirus-driven shutdown of all public schools in the Washington region, and the second day that Elias — who teaches at T.C. Williams High School in Alexandria — filmed an informational morning video for students, streamed live on Facebook.

The Northern Virginia school system announced last week that it will remain shuttered until at least mid-April. During the closure, the 16,000 students of Alexandria City Public Schools are not required to do any academic work, although they are encouraged to complete online activities and follow daily exercises listed in instructional packets.

The closing, Elias said, left many T.C. Williams teachers reeling. They worry their classes will fall behind academically — and they’re desperate to stay in touch with students who they have come to know well, having finished much of the school year.

“Guys, all your teachers are worrying and wondering about you,” Elias told his viewers. “This happened so suddenly. . . . The most important thing is to not stay isolated from school.”

It is a dilemma confronting educators nationwide, as scores of states — 38 as of Tuesday afternoon, according to Education Week — abruptly shut their doors in a bid to contain the virus. The suddenness of the closures left most with little time to prepare an online curriculum, let alone a surefire way to communicate with students.

Elias chose to stream on Facebook, he said, because nearly a decade at T.C. Williams taught him social media platforms are where teenagers spend much of their time. Other teachers are resorting to similar measures — taking crash courses in TikTok, Instagram and Reddit.

Jessica Heppen, senior vice president at American Institutes for Research, a Washington-based nonprofit research group focused on social and behavioral science, said it is not surprising that educators must innovate to stay in touch with middle-schoolers and high-schoolers. Online learning tools have improved, she said, but are insufficient to support a massive national experiment in online education — even if teachers everywhere knew how to use them, which is not the case.

“We as a nation were not prepared for this,” said Heppen, who has studied online schooling in K-12 schools. “So it’s good there are a plethora of tools available.”

Mary Kay Downes, an English teacher in Northern Virginia, is repurposing online learning platform Google Classroom to check in with her students.

Downes — who teaches in Fairfax County Public Schools — sends messages every other day to her two English classes and to students producing the high school yearbook, which she advises. The Fairfax system, like Alexandria City, is not mandating academic work for its 188,000 students during a roughly month-long shutdown.

“Use this time to relax and to read,” Downes wrote March 14 to her senior English class.

“Start a diary or blog,” she suggested Tuesday. “Record this life-altering event so you can one day share it with your children.”

Elsewhere in Virginia, engineering and biotechnology teacher Jennifer Ushe is relying on videoconference program Zoom to keep her students thinking about science, technology and math during the break.

Ushe has lined up guest speakers, each representing a different science- or math-related profession; upcoming lecturers include a physicist, a pediatrician and a microbiologist. She is asking guests to appear on a videoconference for 30 minutes to an hour to discuss their jobs, answer students’ questions and offer career advice.

Ushe hosts the Zoom calls at noon every Tuesday, Wednesday and Thursday, a schedule she plans to follow for as long as the closure lasts. Any T.C. Williams student is invited to watch and to submit questions.

Her first Zoom call Tuesday drew about 50 student viewers, just a handful of them from her class. Engineer Mike Spaeth — holding a yellow coffee mug and wearing a T.C. Williams hoodie — fielded inquiries about his most difficult work assignment, whether engineering is an onerous college major and how students can find work in the field.

“Stay optimistic if you’re having trouble with things” such as differential equations and thermodynamics, Spaeth told the teenagers. “You can do anything; dream big!”

He ended by giving the students his email address and offering to help them find engineering internships. Afterward, Ushe said the first session drew far more viewers than she expected.

“Now, what I really need to do,” Ushe said, “is find someone who works with vaccines and viruses, who can come on and speak to viruses.”

Elias plans to stream his morning sessions, which last about half an hour, every weekday.

The topics, he said, will vary — on Tuesday, Elias began with a weather forecast (“cloudy and rainy”), switched to explaining how students can pick up free meals from the school system, then plunged into a recent reading assignment for his history students, who were learning about the Byzantine Empire when school shuttered.

“So what’s going to happen, you think the Byzantines are going to last?” he asked. “I don’t know, they got the Persians on one side.”

Elias’s class makes up a substantial portion of the viewers, though the broadcasts are targeted to all high-schoolers, and Elias’s audience and reach are growing. Monday’s session drew about 200 students, whether watching in real time or tuning in afterward, and — based on the number of live viewers — Elias expected he would wind up seeing a jump in turnout Tuesday.

During broadcasts, students give feedback and ask questions by posting comments beneath the Facebook video. Teachers can watch, too — in a private Facebook group chat Tuesday, educators typed comments and suggestions, and asked Elias to relay the advice to their students.

Among the recommendations he received from other teachers: Eat oranges to strengthen the immune system, use time at home to read “anything that interests you” — and, from English teacher Emily Yarrison, a suggestion that Spanish-speaking students watch television in English with Spanish subtitles, to hone their language skills.

Other important things to remember, Elias said, include staying indoors to avoid other people, washing your hands frequently and taking the coronavirus pandemic seriously. Just because you cannot see the virus, Elias told the teenagers, does not mean it is not extremely dangerous.

But he interspersed more lighthearted moments, too — at one point joking that months of isolation at home might cause his hair to grow back (he is bald).

Elias compared this odd new phase of his job to becoming a social media star: “Guys, it’s hard being an influencer,” he said. A silver lining of the coronavirus crisis, Elias said, is that he may wind up reaching more students, more directly, than he would have otherwise.