The studies included in this volume describe the process embedded in learning to write in Language Arts, as well as in teaching it and assessing it, focusing on the metalinguistic activity triggered in this process. Because of the latter, they also examine students grammar concepts and the process of learning and teaching grammar. These four objectives are included in the overarching objective of elaborating a theoretical frame that accounts for metalinguistic activity as a social and cognitive activity oriented towards the learning of language use. A qualitative, descriptive, and interpretative perspective is adopted, based on case study and action-research; also, the tenets of sociocultural psychology, contributions from cognitive psychology and functional linguistics, and pedagogic studies concerned with peer and small group interaction in dealing with classroom complexity. The chapters result from the necessary collaboration between researchers and teachers, who contribute their specic knowledge both to the design as well as to the monitoring and analysis of the results of the dierent projects. We believe that the interest of the book lies precisely in this diversity. This book highlights "the remarkable epistemological, theoretical and methodological coherence of the research program in language teaching conducted by GREAL research group over the past three decades." (Jean-Paul Bronckart, from the "Foreword").