In The Teaching Gap, which first brought Lesson Study to the attention of many educators outside Japan, Stigler and Hiebert include revising and reteaching the research lesson as steps 5 and 6 of Lesson Study. When Takahashi and I proposed Collaborative Lesson Research as a powerful form of lesson study, however, we deliberately excluded these steps. Because so many implementations of lesson study include those steps, we should explain our reasoning.

We exclude reteaching the lesson for two reasons. First, as Toshiakira Fujii argues, the research lesson should be your very best effort, because the children deserve nothing less. If you have in mind that you will revise and reteach the lesson, you may feel like it’s ok to try something that is “half-baked”.

Second, revising the lesson as part of lesson study places too much importance on the one lesson. It contributes to the misconception that lesson study is about creating a good lesson, while undermining the more important idea that lesson study is a vehicle for learning something valuable about teaching and learning more generally.

Of course, teachers will almost always revise their research lesson when they teach it later to a different group of students, whether it’s the next day or the next year. That is entirely proper. But that should be considered an outcome of lesson study rather than part of the process.