Based on theoretical studies of the genres and the theory of activity, this paper addresses issues relating to the use of textbooks in Portuguese. We found the relationship between school agents and this mediation instrument, focusing on production of written activities, obtained from classes in a public high school in Rio Grande, RS. The use made of this material was observed considering the evaluation presented by the National Textbook Program and the teachers' knowledge about the textbook. We also observed how such use contributes to the development of students' discursive competence. The results show that there are differences in the use of textbooks as a mediator of text production, depending mainly on the (re) presentation and (re)signification of the teaching objects that compose the discursive nature of the Portuguese textbook genre.
education; Portuguese; textbook; text production