For nearly 20 years, high school chemistry teacher Jonathan Bergmann would teach a lesson in class, help students after school and give them standard homework assignments. He was good enough to win a teacher award. But seven years ago, he and Aaron Sams, another teacher at Woodland Park High School in Colorado, decided to do something different.

The initial impetus was reducing the time kids spend with teachers after school. The result has been a total rethinking of how classrooms operate, all based on a question every teacher should be asking: “What is the best use of our face-to-face class time?” The answer for Bergmann: turning his class upside down.

Today, the 48-year-old helps teachers around the world “flip” their classrooms. Last week, he was at Harvard Law School talking about the virtues of flipping. A book he and Sams wrote, “Flip Your Classroom: Reach Every Student in Every Class Every Day,” is coming out in June, and Bergmann is planning the fifth annual conference on Flipped Learning this summer. He and Sams also are launching a nonprofit organization to train teachers in the concept. He is now the lead technology facilitator for the Joseph Sears School in Kenilworth, Ill.

Here are excerpts of conversations I had with Bergmann on the phone and by e-mail:

Q. What exactly is a flipped classroom?

In the simplest form, basically, it’s this: What’s normally done in class, the direct instruction piece, the lecture, is done now at home with videos. And in class, you, the teacher, help students as they do what they would normally do at home.

So it’s homework in school and lesson at home?

When you are stuck in the old model, kids would go home and do one of three things. If they didn’t understand what they were supposed to have learned in school, they gave up, called a friend or cheated. In the flipped classroom, the teacher is there to help with the instruction piece, the learning, while the lecture is done at home.

Tell me about the videos.

Aaron Sams and I decided to start making videos that we could give kids to take home so they wouldn’t have to spend so much time after school getting help. Our assistant superintendent knew we were doing this with the videos — we called them vodcasts — and he told us, “My daughter is at college and loves podcasts. She said, ‘I don’t have to go to class anymore.’ ” So we had an aha moment. What is the value of class time?

The access issue is big. How did you do it?

We had about 160 kids taking chemistry class, and 30 had no [computer] access. We burned DVDs, handed them out and said, “Push play.” We also burned them onto flash drives. A lot of kids had computers but no Internet access.

So what was the next iteration?

The second iteration was the “flipped mastery” model. We realized that the kids had improved on the tests we gave them. The kids were better by one standard deviation, which is a lot. We were like, “Wow.” Then we realized we were still unsatisfied with our interactions with kids. We wanted to make it better.

In the first iteration, every kid watches Video 5 on Tuesday night, and on Wednesday you do the same activities. We kept the kids on the same page. But one thing that is particularly true in chemistry is that if a kid doesn’t know how to do A, then B is hard and C is difficult and E is impossible. Math is very similar that way. Foreign language, too. What we want kids to do is to master the content. So now, at the end of a unit, a student has to score a minimum on a test. At the end of one unit, not all kids are on the same page. They are in different places. This was wildly successful.

What if the kid doesn’t pass the test? Do they retake the same test?

I had to diagnose what the student didn’t understand, and they had to go learn it and take the test again. No, it was a different test.

Then what happened?

We kept asking about the best use of class time. We realized we were giving the same assignments and experiments and homework. And then we asked ourselves, “Are there better ways for kids to learn these things?” We went back and examined everything we did. Two years ago, we began to say the videos shouldn’t be the focus. The video is just a way for them to learn. Is there another way for kids to do that? Yes, there is. Online simulations, for example. In the science world, there is an open source deal called PHET with free online simulations in different subjects. So now the kids can go to learn the content there. They don’t need to watch my video. You just need to learn the material. Students need multiple ways to access content. A kid would say, “Hello, Mr. Bergmann, do I have to watch the video? Can I read the textbook instead?” We said, “You can learn it any way you like.”

How are kids supposed to know where to go to learn the material?

We give them choices. And then we gave them alternative assessments. Kids can make videos, games, projects to show that they have learned the material.

How has this affected standardized test scores?

Students have done better. I don’t know the numbers, but they learn the material. This really works. In my first 19 years as a teacher, I was a good stand-and-deliver lecture guy. I won a presidential award. I had all these credentials. I was good that way. You get to the end of the unit and a kid gets a 62. We move on. All you can do is say, “Wish you had done better, Joey,” but by that time he’s lost and we are in Unit 2. Joey never really learned it. This forces Joey to learn it.

Are there subjects that are good to have a flipped class and subjects that aren’t?

We started it with the hard sciences, physics and math. It works for foreign language. But we’ve got some amazing teachers speaking at our conference who are English teachers. I always thought that would be harder, but they love it. I haven’t seen a whole lot of social studies and history, but there is a movement amongst them. There’s a guy in Dallas who is an economics teacher who flipped his class. One video the kids watched at home was about supply and demand. The next day in class he asked the students what topic they wanted to discuss. Someone said the Dallas Mavericks. The Mavericks had just won the NBA championship. He said, “Fine,” and started asking if there is supply and demand in the NBA.

Isn’t this a blended model of education? Part online, part face-to-face?

Yes, but it’s more than that. The benefits are huge. Kids learn to become independent learners. They figure out how to learn for themselves. In the old model, who would get the teacher’s attention? The kid who raised his hand, the kid who would do well anyway. In this model, everybody gets the teacher’s attention. It humanizes the classroom.

This makes the role of the teacher at least as important as ever. Right?

The flip makes the teacher more important. The teacher is not the disseminator of knowledge but the chief facilitator and the chief learner.