Despite the norms of privacy that pervade teacher culture and the assumptions of behind-closed-doors independence, teachers actually "need" their colleagues, whether they like it--and them--or not. Teachers are inherently dependent on one another since no one of them alone constitutes their students' education. Students move from teacher to teacher, and it is up to them to make that movement coherent. Acknowledging this interdependence is especially urgent when they consider issues of equity. In fact, that is exactly what educational research has increasingly shown. Given the organization of the school as a workplace, it is not surprising that the collective dimension of teachers' work is often overlooked. In high schools, teachers' preparation time is usually organized to optimize students' choices, not to support teachers' conversation and collaboration. Teachers working in the same subject area or grade level may or may not be housed in similar parts of the school building. They are seldom given paid time to work together to develop a common vision or to discuss shared challenges. Occasionally, teachers are called on to work collectively. Teachers who want to meet and collaborate with their colleagues often do so at great personal expense. Frequently, they end up donating hours before and after school or sacrificing their scant preparation time. Even in places where teachers' interdependence becomes an explicit part of their work, it is seldom adequately offset by any reductions in other time-intensive job duties. (Contains 7 endnotes.)