The methodological approach that we have been developing for over 10 years in the Research Group on Pedagogy of Children Values, at Complutense University of Madrid (Spain) is based on a pedagogical theory of children as active subjects. This article focuses on our last project “Growing up Happy” and addresses two main questions: a) what makes children feel happy, and b) how can we use this information for education. To explore these questions, we put the voices of the children themselves at the center of the research. With the financial support of Fundación Crecer Jugando (Growing By Playing Foundation), we carried out field work at three public and two privately-subsidized Spanish Primary Schools involving students from first to sixth grades. As our interest is in education, our aims were twofold: to learn what children say, believe, and imagine, as well as to make recommendations for educational practice.