The progressive globalization process, in which our world is immersed nowadays, makes it increasingly necessary to cope with new challenges. Learning an additional language has a special relevance in this sense, since the ability to communicate is the first requirement for an individual wishing to engage in a gradually multicultural and multilingual context. This handbook is based on the idea of considering CLIL as an exceptional opportunity for schools to produce critical and creative thinkers with life skills in a context in which their different learning styles are supported by developing their multiple intelligences. The general aim of this book is to find the relationship of how our pupils, in first grade of Primary Education in a British School in Asturias (Spain), develop critical thinking and learn in a mix ability class, and how can we implement our lessons in order to achieve an active methodology in where our learners have to acquire language and content in a CLIL environment. Thus, we are going to take into account Key Competences, Multiple Intelligences, Critical Thinking, Bloom's Taxonomy Theory, and CLIL methodology and assessment.