The purpose of this booklet is to offer guiding principles about learning in the twenty-first century. It is intended for teachers, curriculum designers, school leaders, and others involved in all levels of school education and can be used for any age group, as the principles it contains are general enough to be applied in different contexts. The guide offers a bridge between classroom practice, educational theory, and academic research. It draws on theories developed by researchers and teachers, along with the expertise of educational organizations. Historically, theories of learning, ideas about what teachers should teach, examples of practice, and suggested models have been developed separately by different organizations. The result has been a lack of unity, with little cumulative knowledge and an absence of cooperation on research. This guide attempts to address this lack of unity by responding to the question: What is it that students should be learning in the twenty-first century?