It is called the "flipped classroom," a national trend that is a growing part of the fast-changing world of education as teachers harness the power of digital tools.
Some parents cooking dinner may be surprised to overhear a math teacher's voice explaining a complex formula in the next room. Many are embracing this approach, however, saying it lets students learn at their own pace, saves precious class time, and clears the way for more-engaging group projects.
Teachers in Fort Lee, New Milford, the Northern Valley Regional High School District, and Wayne are among those experimenting.
"It's an up-and-coming concept and really spreading," said Samantha Morra, a technology consultant for North Jersey schools. "It's allowing a shift in how time with the teacher is used."
There are doubters, too. They worry that some students, especially in high-poverty areas, might not have sufficient access to computers. Some also warn that high-tech tools are not magic; students might not bother to watch the videos unless they're naturally motivated. And some teachers are baffled by all the digital devices.
But many are becoming converts.
Carrie Wiederholz, a seventh-grade pre-algebra teacher in Fort Lee, first read about flipped classrooms last summer while on a beach vacation. Now, almost every lunch period, she uses a flip camera to tape a short lesson, usually lasting three to 10 minutes, as she introduces a new unit to her students.
The camera catches her scribbling down equations on her SmartBoard and cracking a few jokes. Her students watch it on their own later, take notes, and try to solve several questions.
The "real meat of the lesson" happens in class the next day, she said, when they review the unit together and try more difficult problems in small groups.
Wiederholz, a 10-year veteran, said this technique means she no longer has to "teach to the middle" because students who struggle can watch a lesson several times and those who grasp it quickly can skip ahead instead of getting bored.
Some watch the videos in the car on the way to sports practices. Students who are home sick can stay on top of their work, and sometimes parents tune in to brush up.
"Every single quiz and test I've had to make harder," Wiederholz said. "I'm setting higher expectations, and they're leaping bounds above it."
Several parents and students agreed.
"This is less stressful because I can rewind," said Shaina DeLeon-Monroe, 13. "I get anxiety over school when I don't get it."
Surging access to laptops, tablets, and smartphones enabled the trend, along with software and apps that let teachers make videos and podcasts easily. Some teachers use free videos already available on sites like SchoolTube, CrashCourse, Ted-Ed, and Khan Academy.
Others, like Wiederholz, prefer making their own, saying students connect better with a familiar face.
Her next project will have students create the lessons themselves.