Lesson study basically involves a bunch of teachers from other schools coming over to your school and watching you teach. After the class (which is a performance like most observations) the kids are sent home and then you and the other teachers talk about your lesson and then discuss more generally 'teaching'.
Sounds pretty neat, huh?
So onto my second Japan related story. One of my favourite comedy programs over there once asked old people (who obviously have lots of life experience) which old sayings were the most useless. One guy said:
Two heads are better than one (lit: three people together have the wisdom of Monji)
The presenter asked him why he thought this was a useless saying and the old guy said 'because if the people are idiots it doesn't matter how many there are'
And so back to lesson study. I distinctly remember receiving some interesting advice from some of the English teachers who were gathered there. I also distinctly remember them telling me that if the kids don't learn good Japanese their English will never be any good (myth) and that educating young kids in English would make their native Japanese 'go weird'(myth). As the teachers were all older and much more experienced than me I had to sit there in silence as they continued on with this kind of 'professional development'.
I'm sure study learning could have some great benefits but the plural of anecdote isn't data.