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 design principles that were developed by a group of educators, practitioners, scientists, and parents, building on the knowledge they have today and the contributions of many in the field to nurture innovations, new models, and new enabling policies. These principles are already being applied in places where innovative approaches to learning have taken root. The companion playbook for schools--"Design Principles for Schools: Putting the Science of Learning and Development Into Action" (ED614438)--lifts up recommendations for both structures and practices as well as powerful examples of how these design principles are currently manifested in leading lights across the country. 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 desired result of the playbooks is to support increasingly robust innovations, new collaborations aligned with the resources for positive growth found in young people's communities and cultures, and a commitment to the reimagining and redesign of education and learning systems in both formal and informal learning settings. [This report was prepared in association with the Science of Learning and Development (SoLD) Alliance.]