INTRODUCTION

A few months ago, a teacher named Jen Brimming1 sent us a video of her year 7 (sixth-grade) English classroom at Marine Academy in Plymouth, England. Members of our team had been meeting occasionally with Jen and her colleagues over the previous few months to share and study teaching videos so we weren't surprised to hear from Jen or even get a video from her. But getting a video like the one she sent-that was a surprise. The video was almost eight minutes long and was like a perfectly crafted Swiss watch; each interaction meshed seamlessly into the next with flawless timing and execution.

Celebrating Jen's lesson video for its length as well as its quality might seem odd at first, but duration is surprisingly important.

A short video can be powerful in demonstrating a technique or in modeling a solution to a specific teaching challenge-for example, how teachers might use Cold Call so it's positive and inclusive, or how they can correct an off-task student in a way that is both clear and supportive. But only a longer video can give viewers a mental model of how a lesson (or at least an extended portion of the lesson) should look and how a dozen or more pieces can fit together and balance one another.

There is more to effective Cold Calling, for example, than just the Cold Call itself. To master the technique, to make it and your teaching more broadly sing, you'd need to have a sense for how frequently to Cold Call and what other forms of participation to use to balance it-for example, how using Turn and Talk before a Cold Call could let students rehearse and prepare, or how a brief period of writing before the Cold Call could allow you to choose especially relevant answers to begin the conversation. But also you'd have to master not using Cold Call. This too would be important: how sometimes asking for volunteers instead could socialize eager and energetic hand raising. After all, one good reason to Cold Call is that it has the effect of causing more students to volunteer more often. So sometimes you'd want to let students have the chance to show you-and just as importantly, their peers-that they wanted to answer your questions. There are questions of rhythm and timing, variation and consistency, balance and pacing and spacing. Success is a result of the moments when any technique is not used as much as when it is-of moments when something else is called upon because it is the key that fits the door you're standing in front of.

So even while proficiency can come from seeing the details of a technique in focused examples-short clips might in fact be the best way to get to proficiency-mastery comes from seeing how the technique sits among other techniques in the larger arc of the lesson. A short video can show you how to make your Cold Call positive and inclusive, but you need a longer video to show how often and in combination with what else is optimal over the course of 10 minutes of teaching vocabulary, say. Plus the right pattern and dosage might be different when you switch from vocabulary instruction to book discussion.

You could call that sense of what the big picture ideally looks like and how the pieces fit together a mental model, and when teachers have a strong mental model, they master individual techniques faster and put them into service more effectively and flexibly. Mental models are critical in other learning settings too, and examples can help us understand why they are critical in teaching.

A coach could teach you to pass and dribble a ball, for example, but until you'd seen an elite team play-until you had a mental model of how Barcelona or the Golden State Warriors looked when they did their thing-you'd be unlikely to know just how to link your skills together and choose among them. You'd dribble at the moment you should be passing, perhaps, and even if your dribble was technically proficient in all the important ways, maybe even better than proficient, it would still not be a pass. You'd need to know whether to dribble or pass in a given setting and, further, what the rhythm of dribble and pass was, what a typical dribble-to-pass ratio was and how it changed in different game situations. Champions are the ones who can sense how to tweak the model late in the fourth quarter with the game tied and the other team pressing.

Or you could learn to play notes fluidly on the cello and add an array of flourishes, but hearing how a virtuoso brings a sustained section of a concerto to life, noting how she applies those tools to create meaning and expression, to tell a story in notes, sometimes in ways you had not thought of, the way the spacing between notes lingers just a touch in a certain section, perhaps even in ways that you can't quite explain-that is part of how you come to find your own unique style. Your final interpretation would not be (and would not aspire to be) the same as hers but you would now have a vision for how things come together, how notes can be made wistful. We observe that seemingly every garage band, no matter how humble, is ready to cite their "influences." But we forgive their enthusiasm. The mental models they have gleaned from others are precious to them.

We, your four authors, all have a series of techniques we love to use when presenting: Cold Call, of course, but also Turn and Talk and quick bursts of Formative Writing called Everybody Writes. And we love to build the energy in the room and then ask for volunteers and see a sea of raised hands.

We select from among these constantly, planning some of the decisions into our sessions but always adjusting the plan in real time. We'll think: we've used too many Cold Calls and it feels a bit like they are discouraging hand raising; there are lots of raised hands but now we think it might be better if participants slowed down and wrote their thoughts. The Turn and Talks were great but now we're in danger of overusing them. Sometimes the moment is ripe for a bit of direct instruction to feed knowledge that will support later discussion and analysis. We do this because something is telling us throughout the session: It's too quiet; we're not engaging everybody; it could be more rigorous; we need to pick up the pace. We're homing in on a signal, steering toward a goal and forever adjusting our course. We make our tiny (or large) corrections because something feels not quite right.

The "something" that is telling us what it should look and feel like in the room is our internalized ideal, the mental model we each hold in our mind. To be clear, this ideal is different for each of us, though also similar in many ways. And the model each of us is using changes slightly depending on what, where, and when we're teaching. We make our decisions to hew closer and closer to an evolving model. And the model (or models) will help us to make stronger decisions. We ask, "Is this lesson going well?" and answer by comparing what's in front of us to an ideal, or a range of ideals, kept in our mind's eye. This ideal reflects not only what we think is optimal but what is possible. Often we can imagine it because-and sometimes only because-we've seen someone do it. We are what we have seen.

Which brings us back to those eight minutes of brilliant video we received from Jen. We were excited not only to have an example of individual techniques executed with insight and precision, but to have a model of how those techniques could work together. And we were doubly excited because we knew that Jen's intent was not only to share with us but to share with her colleagues. She had set out to try some new ideas and share them through video. She had filmed her own classroom as a first step to developing a schoolwide vision, and just maybe also a culture of constant self-reflection. Given how intentionally she and her colleagues were using video to guide their professional study, we thought it would be useful to talk a bit more about the power of video as a tool. And then, we promise, we'll show you Jen's video!

VIDEO IS THE MODELING TOOL

Video is perhaps the most powerful tool for building mental models, and its proliferation is a hugely significant and, frankly, underexamined change in teacher professional development. In the past 10 years or so, video has become dramatically more available, with the cost in terms of time, money, and logistics at a fraction of what it only recently was. What once required hiring a videographer with a large and expensive camera2 now requires only a phone or a tablet on a table at the back of the room. Back then, you needed to wait a week or two for the videos to be produced and probably would have to wheel a DVD player (remember DVDs!) into your room to watch the resulting footage. Editing that video yourself was all but out of the question. Now your colleagues can text to your phone the video they shot an hour ago on theirs and you can send them what you shot on yours. You watch it on your free period an hour later, and then again at home that evening, assuming you can find it amid all the internet cat videos it's competing with. You can edit the key moments on your laptop-possibly your phone as well-and share it with a mentor or a mentee. Suddenly, what was a luxury has become a commodity. It's everywhere and everyone-you included-has a tool for creating mental models. Away you go.

Or at least, potentially. We say potentially...