Turning around a low-performing school is a complex process in which cause-effect relationships are difficult to isolate. But recent interest in helping low-performing schools--spurred on by the reforms mandated by the No Child Left Behind Act--has generated some useful research and thoughtful analysis. This digest explores some of the key insights from that literature. The digest first discusses how low-performing schools are defined: recently by failure to achieve state-mandated accountability targets, particularly test scores. Next it discusses why schools perform poorly, focusing on three prominent matters: demographics, insufficient resources, and ineffective school practices. The next section of the digest discuses sanctions and their effects on low-performing schools. This is followed by discussion of how external assistance, from the state or district, can help low-performing schools, noting three promising practices: (1) providing technical assistance; (2) aligning policies and practices with academic goals; and (3) allocating resources to support achievement. Finally the Digest discusses the principal's role in turning around a school's overall performance. (Contains 12 references.) (WFA)