This paper aims at reflecting on the theoretical-practical relation in the ongoing formation of the teacher of first language. It focuses on the mobilization of knowledge about writing and evaluation of texts by three subjects, in a practicing activity of text evaluation, applied after the presentation and discussion of contemporary linguistic theories about the theme. The analyzed results show two positions of the subjects, concerning the effect of theoretical knowledge just-acquired about the practicing of text evaluation: one of them preferred the established situation, with an evaluation centered on the normative aspects of writing; and the other two showed a transitional situation, with the introduction of criteria of textual-base evaluation.