This book seeks to provide a theoretical-methodological approach so that teachers of Physics, Chemistry and Mathematics in Secondary Education can effectively plan the teaching-learning processes. It deals in detail with reasoned planning and active methodologies, it explains the levels of didactic planning and it delves into the importance of contextualization in context-based teaching. The main objective of the book is to provide teachers with useful tools and strategies to improve the quality of education in these areas, taking into account the specific characteristics of the students and their environment. The book offers a practical guide for the planning of teaching-learning processes, ranging from the definition of objectives to the choice of activities and the evaluation of the process. In addition, examples and case studies are included to illustrate the theoretical concepts, which makes the book very accessible and useful for teachers. In summary, this is a valuable book for teachers of Physics, Chemistry and Mathematics in Secondary Education who wish to improve the quality of their teaching.