Because researchers know so much more about the brain and development than they did when the 20th-century U.S. education system was designed, this knowledge can now be used to design a system in which all individuals are able to take advantage of high-quality opportunities for transformative learning and development. This playbook suggests a set of engineering principles that were developed by a group of educators, practitioners, scientists, and parents, building on the knowledge we have today and the contributions of many in the field to nurture innovations, new models, and new enabling policies. At their foundation, the design principles are intended to advance the following goals for youth learning and development: (1) Learners can think critically and creatively to solve complex problems; (2) Learners deeply understand content and can apply their knowledge beyond the classroom; (3) Learners are self-aware and engage meaningfully with others; (4) Learners hold a positive sense of identity, self-potential, purpose, and direction; (5) Learners make healthy life choices; and (6) Learners are empathetic, ethical, and proactive in contributing to the welfare of their communities. The playbook includes a set of design principles--informed by the Guiding Principles for Equitable Whole Child Design--to achieve these goals, along with recommendations for evidence-based structures and practices that further these aims in k-12 learning settings. The Guiding Principles for Equitable Whole Child Design is the organizing framework to guide transformation of learning settings for children and adolescents and is reflected in five elements: (1) Positive Developmental Relationships; (2) Environments Filled with Safety and Belonging; (3) Rich Learning Experiences and Knowledge Development; (4) Development of Skills, Habits, and Mindsets; and (5) Integrated Support Systems. The desired result of the playbook's design principles is to have increasingly robust innovations, new collaborations aligned with the resources for positive growth found in children's communities and cultures, and a commitment to the redesign of education and learning systems in both formal and informal learning settings. [This report was co-published by Turnaround for Children and prepared in association with the Science of Learning and Development (SoLD) Alliance.]