This EdSource report summarizes the Initial Findings issued in October 2005 from a two-year study conducted by EdSource, Stanford University, University of California-Berkeley, and American Institutes for Research (AIR). In addition, this report includes information collected during the study but not previously reported (from superintendent interviews and principal open-ended questions) as well as the results of an additional analysis conducted on curriculum program choice and association with Academic Performance Index (API) scores. The study found that four specific domains, or clusters of practices, were most strongly correlated with higher school API scores: (1) prioritizing student achievement; (2) implementing a coherent, standards-based instructional program; (3) using assessment data to improve student achievement and instruction; and (4) ensuring the availability of instructional resources. The remaining three domains examined--involving and supporting parents, encouraging teacher collaboration and professional development, and enforcing high expectations for student behavior--had much weaker but still positive correlations with school performance.