The promise of education reform is that all children will receive a quality education. However, there are enormous challenges to reform, including resource inequities, an aging teaching force, and public doubts about school effectiveness. Moreover, school reform policies place enormous strain on teachers and students. Teachers need to implement new curricula and ensure that they are providing appropriate instruction. Students--including English language learners--must learn challenging content and pass statewide assessments in order to graduate in many states. These new demands coincide with the well-documented changing face of the U.S. student population. More teachers are responsible for the education of children from diverse backgrounds--children who speak little or no English upon arrival at school, children who may have had interrupted schooling in their home country, and children whose families may have had little exposure to the norms of U.S. schools. In general, the U.S. teaching force is not well prepared to help culturally diverse children succeed academically and socially, because preservice teacher preparation programs have not offered sufficient opportunities for learning how to teach culturally diverse students. As a result, many teachers have been learning on the job. Fillmore and Snow (2000) assert that teachers need an understanding of educational linguistics--how language impacts teaching and learning--to do their work well. They argue that knowledge about language will enhance teachers' practice in general, and in particular, it will aid them in teaching literacy. This digest focuses on principles and structures for professional development of practicing teachers that can help them gain the knowledge they need about language and on some challenges to overcome for providing good professional development opportunities. (Contains 11 references.) (VWL)