Goddard and colleagues conducted a study in a large urban school district in the Midwest. First, the researchers surveyed 452 teachers in 47 elementary schools to determine the extent to which they worked collectively to infl uence decisions related to school improvement, curriculum and instruction, and professional development. To determine the relationship between teacher collaboration and student achievement, the researchers used reading and math achievement scores for 2,536 fourth-graders, controlling for school context and student characteristics such as prior achievement. They found a positive relationship between teacher collaboration and differences among schools in mathematics and reading achievement.