Recent intervention research has demonstrated success in raising the achievement level of students who are struggling with mathematics. This practice guide, developed by the What Works Clearinghouse™ (WWC) in conjunction with an expert panel, distills this contemporary mathematics intervention research into six easily comprehensible and practical recommendations for teachers to use when teaching elementary students in intervention settings. Two federal laws, the Elementary and Secondary Education Act (ESEA) and Individuals with Disabilities Education Act (IDEA), require use of instructional practices supported by evidence. The recommendations presented in the guide address these laws by translating the body of high-quality evidence into actionable practices for teachers to use with their students. Although this guide is an update of the 2009 guide, "Assisting Students Struggling with Mathematics: Response to Intervention (RtI) for Elementary and Middle School," it is narrower in scope, focusing only on practices and principles underlying effective small-group interventions in grades K-6. The practices that appear in this guide's recommendations highlight effective approaches to mathematics intervention that meet the needs of the students in small-group or one-on-one settings. Each of these practices move students toward more fluent performance of mathematics. Each recommendation includes features of intervention and/or instructional practices, with guidance on how to implement them, advice on how to overcome potential obstacles, and a short summary of the research evidence that supports the recommendation. This guide is designed to be used by teachers providing mathematics intervention to students who are struggling. This professional group includes special educators, mathematics general education teachers, mathematics specialists, and mathematics coaches. [For the 2009 edition of this guide, see ED504995.]