The teacher is both the protagonist and the director of the performance; the classroom is the set. The script is the lesson plan and the learning materials are the props.
It's like improv. theater because the students don't have scripts -- or at least, some of them don't. The teacher's challenge is to respond to the improvisions the students throw his/her way. The goal is for the teacher to remain in character -- and continue to teach!
In this staging, the teacher controls the setting (environment), the script, the props, and stage directions. S/He has some control over the pacing of the lesson - but not total control because the students' improvisations can easily throw things off balance.
As a teacher gets to know the students in the class better, s/he is better able to predict what kinds of improvisations the students might throw into the mix. Generally speaking, if the relationship between the teacher and students is respectful, the improv comments/behaviors of the students may actually enhance the lesson and cause the learning to soar to a different height or along a parallel path that provides additional insight for all.
Those items the teacher can control (setting/environment, script, props, and stage directions) can easily affect the quantity and quality of the improvised role of the students.
In the next week or so, we'll be taking a closer look at each of these pieces.