This booklet summarizes research on best practices for implementing successful small learning communities and career academies. When well implemented, improvements in instructional and personalization strategies in combination with structural supports have demonstrated improved student attendance and learning. "From High School to Learning Communities--Five Domains of Best Practice" brings together a knowledge base, tools, and resources for implementing and deepening small learning community practice. Its aim is to provide guidance to school staff and stakeholders in the demanding work of transforming 20th-century comprehensive high schools into 21st-century learning organizations. The five domains detailed are: (1) Interdisciplinary Teaching and Learning Teams; (2) Rigorous, Relevant Curriculum and Instruction; (3) Inclusive Program and Practices; (4) Continuous Program Improvement; and (5) Building/District-Level Support for Small Learning Communities (SLCs).