To support school improvement efforts, school leaders and education agencies might need to identify groups of schools that are similar so that schools can compare their performance or share practices with other schools in the same group. This could also allow education agencies to provide tailored supports to schools in a group. This guide describes how an education agency can select a distance measure (a statistical rather than a geographic measure) to identify schools that are similar to a target school, using a variety of characteristics that enable school leaders to better understand their schools' relative performance. This guide is based on work done with the Nebraska Department of Education and is designed to help staff in other education agencies who are interested in implementing a similar approach to support school improvement.