This book summarizes the results of a multimethod project on school development performed during the COVID-19 pandemic. It combines innovative theoretical approaches and findings as well as long-term online research activities in which student assessments delivered the bases for adaptive teacher trainings. The theoretical foundations relate to sustainable conditions of classroom and school development, an approach to personality development, and a focus on instructional coherence. Empirical findings concern the development of learning-strategy use and classroom needs over time as well as a model for effective teacher education and related course evaluations. A further research area concerns advanced perspectives from digital-learning research, such as the effects of social media in classrooms, mixed and virtual learning materials, computer-based collaborative learning, and innovative interventions in media research. The book is aimed at researchers, teacher trainers, instructional designers, and practitioners in the field of school development as well as teacher education.