"Professional learning communities," the name given to teachers' collaborative professional learning--or PLCs, as they are often called--has become so overused that the term's meaning is often lost. Only when teachers reflect on their instructional practice, consider the effect instruction has on students, and implement insights gained from a meeting to improve their teaching performance, can this process be called a professional learning community. This issue of "SEDL Insights" explores ways that education leaders can guide their staff in the implementation of effective PLCs.