From noted authorities, this book presents a comprehensive approach to designing and implementing evidence-based Tier 3 behavior interventions for K--12 students. The authors' functional assessment-based intervention (FABI) process has been supported by multiple peer-reviewed studies conducted in authentic educational environments. Step by step, chapters spell out proven methods to define target behaviors, determine the function of the undesirable behavior, identify appropriate replacement behaviors, and deliver and monitor intensive interventions. Illustrated with real-world case examples, the book shows how to embed FABI within a school's integrated tiered system of supports. Guidance for scaling FABI district- and statewide is also provided. Ethical issues, professional standards, equity concerns, and cultural and linguistic considerations are addressed throughout. In a convenient large-size format, the book includes reproducible checklists and forms that can also be downloaded for ease of use.