The National Writing Project is probably the largest in-service group in the country. They got their start in the Bay Area in San Francisco back in the 1970s as a grassroots movement bringing teachers together to improve how they taught writing. There are some very interesting features about it that I think are phenomenal.
One of those is the “teachers teaching teachers” model. They will hold a summer workshop each year where teachers come together, they talk about writing, they share their very best lessons with each other, and they form a community. And often that community lasts much longer than the summer; you become a part of something that’s much larger. You’re developing a community of writers who are engaged and enthusiastic about teaching children to write.