One of the most underused resources available to educators is the community of colleagues with whom they work. Such communities are invaluable when they work well because a great way to learn and develop as a professional is to do so in partnership with others who are doing the same thing. The importance of educators learning together is now so clear that the February 2009 issue of Educational Leadership was devoted to ways in which collective learning can take place. For instance, Ruth Chung Wei, Alethea Andree, and Linda Darling-Hammond, in their article "How Nations Invest in Teachers," consider several countries that score high on international measures and report that professional development programs in those nations provide time for learning and collaboration, offer job-embedded professional development, and encourage teacher participation in decision making. And, in their article "Teacher Learning: What Matters?" Darling-Hammond and Nikole Richardson argue that teacher professional development should be a sustained effort, should be integrated with school improvement, and should include professional learning communities. A similar philosophy has emerged in the corporate and nonprofit worlds, where one of the most powerful forms of professional development is a "community of practice" (Lave & Wenger, 1991). In education, working together in this way extends beyond learning to dealing with practical issues that affect us collectively and individually, such as determining how best to use resources or clarifying the path that a school should take. It really helps to work things through with colleagues, both formally and informally. - Introduction.