In order to comply with the Individuals with Disabilities Education Act (IDEA) 2004, states must collect valid data as needed to report annually to the Secretary of Education. This requirement, combined with those set forth in the No Child Left Behind (NCLB) legislation, has led states to collect and analyze data about their programs, districts, schools, and student performance and take actions based upon the results. The proliferation of educational data and the increased dependency on those data have put educators in a challenging position. Because critical decisions are made and actions taken based on the data, it is imperative that these data are reliable, valid, and correctly interpreted. As evidenced in the State Performance Plans and discussed in the National Governor's Association's Graduation Counts document, high school graduation and dropout data are often not collected in a consistent manner, nor are the data reliable. To improve the state of affairs of high school data, the procedures used in collecting, analyzing, and comparing the data should be consistent. This will permit educators to make valid comparisons as well as assessments of states' performance over time. Insights gained through such comparisons can help educators and stakeholders identify needs as well as strengths that can be capitalized upon to make positive changes that improve outcomes for youth with Individualized Education Programs (IEPs). Some of the issues described in this document are within the control of states. These include the type of dropout or graduation calculations employed by each state, the exact dates of data collections, and the manner in which educational data are stored. Other factors have arisen from differences in definitions and requirements specific to various federal laws and regulations. The purpose of this practice guide is to discuss several of the factors that caused difficulties with states' data and suggest some practical solutions. The content is designed for state education agency personnel, including special education directors, data managers, and program developers. The National Dropout Prevention Center for Students with Disabilities' SPP Tool Kit Series are practical guides intended to assist state education agencies in their development and implementation of improvement activities associated with school completion. This guide is the first in the series.