Christian Kelly-Sordelet was leading his HB Studio class onstage combat through leaps and tumbles. He demonstrated uppercuts and parries, and how to pretend to be hit. He showed how not to obscure your face from the camera when making a slashing motion with a stage knife.

That last bit, useful for movie and television work, was particularly apropos: This was a Zoom class and students were watching on their screens. And with everyone stuck at home, the weaponry got creative. There was a rolled-up magazine, something that looked suspiciously like a pen and a particularly intimidating spatula.

Like so many social interactions these days, acting classes have moved online. This was, at first, daunting to even the most experienced teachers.

“We were all really scared,” Austin Pendleton said of his fellow instructors at HB Studio, in Greenwich Village. “We had tutorials every day.”

There have been complications — in addition to worrying about their lines, actors now must troubleshoot frozen screens and disagreeable laptop mics — but for many the online experience is proving challenging in a good way. “I think I’m learning a lot from this — I just don’t yet know what it is,” added Pendleton, who has been with HB Studio since 1969.

Reacting to a scene partner’s body language and expressions is an integral part of learning how to act. Zoom, clearly, isn’t optimal in that department. But certain rules were followed in the classes I sat in on: Students turned off their audio and video feed unless they were performing a scene. When two people rehearsed a scene, they disabled their self view so they could see only their partner. And students were finding ways to make the most of it.

Portraying the closeted headmistresses in an excerpt from Lillian Hellman’s “The Children’s Hour,” Krista Magnusson and Amanda Fox used their surroundings and props: Magnusson arranged books on a shelf, Fox looked as if she were grading papers or writing down notes.

“Anything you play is always about the other character,” Pendleton said after the class. “This is where Zoom helps because all you see onscreen is your partner. The world goes away.”

“I was surprised in yesterday’s class by how connected I felt to my scene partner,” said Magnusson, who lives in Vancouver, British Columbia. She had studied with Pendleton in 2018, and when HB Studio announced its spring term would be online, she jumped at the opportunity to work with him again. (Another HB alum, Lawrence Ong, attends Carol Rosenfeld’s course from Shanghai, where the three-hour sessions start at his 10 p.m. The virus may have stopped international travel but it has not stopped international exchange.)

Mercedes Ruehl, the Tony and Academy Award-winning actress, said her HB Studio students “instinctively pitched to the small screen so they became more nuanced, more private, more intimate as actors.”

“The flick of an eye can make a difference,” she added. “I didn’t have to say anything — they were like homing pigeons.”

An essential part of any educational process is feedback, and that seemed to work online much the way it works in person, dependent on each instructor’s style. Pendleton tended to give notes in the form of anecdotes pulled from his extensive acting and directing career, leaving it to the student to figure out how the anecdotes could be applied. Ruehl was more granular, giving directions on inflection and rhythm, and even where to look. When a student was supposed to whisper and slipped into a regular speaking voice, Ruehl requested the exercise be repeated; she also invited comments from her group.

Online teaching actually suits the acting pedagogy of Uta Hagen, the influential actress and author who was a mainstay at HB Studio for decades. She insisted on “psychological realism and using the self authentically,” Edith Meeks, HB’s executive and artistic director, said an email. “We use the real physical, emotional, sensory relationships of our own lives to test the authenticity of the relationships we create to tell the story of the play. Zoom does allow an intimacy that lets us see into one another’s spaces.”

While nobody is arguing that remote technology can make up for people sharing a room — a vital part of acting, even for film or television — it allows for flights of fancy that are not dissimilar to performing in front of a green screen.

“We were doing some Ibsen and someone put a picture of a fjord as their background,” said Evan Yionoulis, the Richard Rodgers director of the drama division at Juilliard, adding that students were even finding ways to do some tricks: “Somebody spills water on one side and the splash comes in another square.”

But Yionoulis said that class is still “about doing the work of acting — you can really tell if somebody is talking and listening, even on Zoom.”

At least the HB folks knew what they were getting themselves into; they started the spring term directly on Zoom. At Juilliard and scores of other schools across the country, faculty and students had to adjust quickly.