In an award-winning study of the Pittsburgh Public Schools, Dr. Leana found that in the schools where teachers talked to each other the most about their jobs, and where the principals did the best job of staying in touch with the community, students had noticeably higher reading and math test scores.
Says a lot about the "ledge" angst explored in this dan/tmao/frizzle. I don't think a radical solution (to this particular issue at least) or, for the love of God, merit pay, is necessary. I'm particularly partial to looking at student work. Critical friends groups and lesson study are also good models.