The National Forum on Education Statistics convened the Data Disaggregation of Racial/Ethnic Subgroups Working Group to identify best practices for disaggregating data on racial/ethnic subgroups. This guide is intended to identify some of the overarching benefits and challenges involved in data disaggregation; recommend appropriate practices for disaggregating racial/ethnic data in districts and states; and describe real-world examples of large and small education agencies disaggregating racial/ethnic data successfully. The working group hopes that the discussion and recommendations in this resource will help state and district staff better understand the process of disaggregating data in the field of education, determine whether data disaggregation might be an appropriate analytical tool in their communities, and, if so, how they can successfully institute or advance a data disaggregation project in their agencies. Disaggregation of student data refers to breaking down data about a student population into smaller groupings, based on qualities or characteristics such as gender, racial/ethnic group, or family income. Educators need both high-level data summaries as well as disaggregated data that accurately describe smaller groups of students they serve. The guide is organized into the following chapters. Chapter 1, Introduction to Data Disaggregation in Education Agencies, explains the purpose of the document; describes the concept of data disaggregation for racial/ethnic subgroups; discusses why the issue is becoming increasingly important in many communities; refers to current U.S. population data; and provides a case study of why this type of data collection can be important and advantageous in a school district. Chapter 2, Strategies for Disaggregating Racial/Ethnic Data Subgroups, recommends specific strategies for disaggregating data, including tasks undertaken during the two major phases of the effort: (1) needs assessment; and (2) project implementation. Finally, Chapter 3, Case Studies, offers an in-depth look at how the disaggregation of racial/ethnic subgroup data is already being implemented through a wide range of state and district case studies. A list of references and related resources is included.