Building foundational whole-number knowledge can help put K-5 students on the path to academic success and career readiness. Filling a gap for school practitioners, this book presents step-by-step guidelines for designing and implementing classwide, small-group, and individual interventions for mathematics difficulties. Effective procedures for screening, assessment, intervention selection, and progress monitoring are described and illustrated with detailed case vignettes. User-friendly features include 20 reproducible handouts and forms; the print book has a large-size format with lay-flat binding for easy photocopying. Purchasers get access to a Web page where they can download and print the reproducible materials. This book is in The Guilford Practical Intervention in the Schools Series, edited by T. Chris Riley-Tillman.