The teaching of grammar in secondary education in general has been one of the most discussed aspects of language teaching. Among other controversial issues, it is questioned whether its teaching improves students' communicative competence. In this paper we will argue that the notion of CONSTITUENT contributes to the good development of the students' linguistic competence insofar as it makes visible one of the mechanisms that language has to articulate the relationship between form (syntax) and meaning (semantics). It is also understood that, in order to achieve this purpose, the approach to grammar at school must be reflexive, pedagogical and implicit. The ultimate goal of this research is thus twofold. On the one hand, a reflective model of grammar teaching is defended; on the other hand, an example of what this type of teaching can be like is offered through the concept of CONSTITUENT. The consequences of this approach are twofold: linguistic reflection and this notion lead thelearner to understand the relationships between semantics and syntax, and, therefore, to believe that he/she understands texts better; and meaningful learning.