Instructional Leadership in Secondary Schools Across the Border examines how principals of Indonesian schools in Malaysia lead teaching and learning amid cultural differences, limited resources, teacher workload, parental involvement, and the need to preserve Indonesian identity and character. Grounded in instructional leadership theory and real school experiences, the book highlights how principals manage instruction, support teachers, engage parents and communities, and respond to practical challenges while maintaining student achievement. It also introduces a context-specific leadership framework that combines academic excellence, character education, adaptive leadership, collaboration, communication, digitalisation, and effective resource management. This book offers practical and scholarly insights for school leaders, teachers, researchers, and policymakers seeking to strengthen educational leadership in cross-border and multicultural school settings.