Résumé : Au Québec, la situation en termes d’apprentissage des savoirs grammaticaux, et surtout de mobilisation de ces derniers en situation d’écriture, est inquiétante. Pour rendre son intervention plus efficiente, l'enseignant peut choisir une approche pédagogique déductive (explication d'un concept suivi d'exercices) ou inductive (observation d'exemples avant la vérification d'hypothèse et les exercices). Notre objectif principal est d'évaluer les incidences d’une intervention éducative en grammaire selon des approches pédagogiques inductive ou déductive sur l’apprentissage par des élèves de 1re secondaire du complément du nom et son impact dans le développement de la compétence savoir écrire. Notre objet d’enseignement, le complément du nom (CN) est un concept de la grammaire actuelle, dont les caractéristiques facilitent son utilisation réfléchie en rédaction, surtout lors des phases de révision et de réécriture. Une méthodologie mixte de recherche a permis de recueillir des données auprès d'un échantillon de 269 élèves de première secondaire, de même qu’auprès de trois enseignants. Pour cette recherche exploratoire d’épistémologie pragmatique, nous avons réalisé des tests de connaissances, des analyses de rédactions et des entrevues auprès d’élèves et d'enseignants. Les résultats obtenus aux tests de connaissances nous montrent qu’il n’y a pas d’écart significatif entre l’amélioration des élèves ayant vécu l’approche inductive et ceux ayant vécu l’approche déductive, si ce n’est d’un léger avantage en ce qui concerne les accords pour les élèves ayant vécu l’approche déductive. Ce qui a par contre émergé de cette expérimentation est d’une part l’effet évident de l’apprentissage des CN sur leurs mobilisations en écriture, peu importe l’approche. D’autre part, les élèves ayant eu une forte amélioration ont confirmé que pour une approche ou une autre, leur implication cognitive demeure l’élément fondamental de l’efficacité de l’intervention éducative. Nous pouvons donc conclure qu’une approche n’est pas significativement supérieure à l’autre dans le cadre de l’enseignement des CN, mais que l’enseignant doit adapter son approche à la situation en tenant compte du contexte, des apprenants et des aspects de l'objet concernés. // Abstract : The choice of an educational approach by a teacher is a significant factor on student achievement. In Quebec, the situation in terms of apprentissage of grammatical knowledge, and especially using that knowledge in writing situations, is worrying. The success rate for the ministerial writing tests graze 60 %. One possible taxonomies to distinguish pedagogical approaches to teaching grammar lies between the inductive and deductive approaches. Our project has for main objective to assess the impact of an educational intervention according to inductive or deductive teaching approaches on learning, by high school students, of a grammar concept (complément du nom) and its impact on the development of writing competencies. In research, if the deductive approach always results, by the teacher explaining a concept, and the students practicing and being evaluated, the inductive approach is defined differently by the authors. For methodological considerations, and because it's a school tradition, we chose to consider an explicit approach focused on the discovery rather than a more implicit approach. Our teaching object, the « complément du nom » (CN) is a concept of the current grammar, including morphological, semantic and syntactic features, should facilitate thoughtful use for writing, especially during phases of revision and rewriting. For all these reasons, this(?) teaching is relevant of a competency-based program, especially since most of the concept notions are provided in Secondary 1 program by the « Progression des apprentissages » (MELS, 2010). A mixed research methodology was used to collect data from a sample of 269 students from eight classes of Secondary 1 , and of three French teachers. For this exploratory research, we used knowledge tests , reviews process marks by the students on writing productions, and interviews with students and teachers in order to document the impact of the teaching sequences, in terms of knowledge learning and 7 mobilization in writing productions. The comparative approach we used allowed us to assess the extent and nature of learning, according to our independent variable (the deductive and inductive teaching approaches), but also on the interrelation between this variable and other aspects of the educational intervention. The test of knowledge scores show that there is no significant difference between the improvement of students who lived an inductive approach and those who lived the deductive approach, except a slight advantage as regards as morphological characteristics for students who lived the deductive approach. What has emerged in this experiment is firstly the obvious effect of learning on their CN mobilizations in writing, regardless of the approach. On the other hand, students who had a strong improvement confirmed that with an approach or another, their cognitive involvement are fundamental to the effectiveness of the educational intervention. Finally, the quasi-experimental context has limited professional actions of the teachers, and at the same time limited their ability to adapt teaching situations. Those who chose to take certain liberties with the scenarios provided, by professional considerations, are those who have seen the results of their students rise, and that, regardless of the pedagogical approach. We can therefore conclude that an approach was not significantly superior to another for teaching of CN in High school, but the teacher must adapt his approach to the situation, taking into account the context, the learners and the aspects of the learning object.