The purpose of this practice guide is to help K-12 teachers and administrators use student achievement data to make instructional decisions intended to raise student achievement. The panel believes that the responsibility for effective data use lies with district leaders, school administrators, and classroom teachers and has crafted the recommendations accordingly. This guide focuses on how schools can make use of common assessment data to improve teaching and learning. For the purpose of this guide, the panel defined common assessments as those that are administered in a routine, consistent manner by a state, district, or school to measure students' academic achievement. These include: (1) annual statewide accountability tests such as those required by No Child Left Behind; (2) commercially produced tests--including interim assessments, benchmark assessments, or early-grade reading assessments--administered at multiple points throughout the school year to provide feedback on student learning; (3) end-of-course tests administered across schools or districts; and (4) interim tests developed by districts or schools, such as quarterly writing or mathematics prompts, as long as these are administered consistently and routinely to provide information that can be compared across classrooms or schools. This guide includes five recommendations that the panel believes are a priority to implement: (1) Make data part of an ongoing cycle of instructional improvement; (2) Teach students to examine their own data and set learning goals; (3) Establish a clear vision for schoolwide data use; (4) Provide supports that foster a data-driven culture within the school; and (5) Develop and maintain a districtwide data system. A glossary of terms used in the report is included. Appended are: (1) Postscript from the Institute of Education Sciences; (2) About the authors; (3) Disclosure of potential conflicts of interest; and (4) Technical information on the studies. (Contains 7 tables and 2 figures.)