Ecuadorian public high school students do not work with textbooks in most rural areas, which does not provide appropriate input for developing language skills. It contrasts with the Ecuadorian National English Curriculum's statement that including CLT is one of the fundamental approaches to underlying teaching practices. Additionally, one of the local concerns of public education is the lower English language proficiency that students maintain when they complete the three years of baccalaureate. Therefore, providing students with alternative resources that engage them to develop communicative skills is one of the primary challenges for teachers. Thus, this current study aims to determine the effectiveness of a methodological guide based on the CLT approach to foster communicative competence in first-year baccalaureate students in a public high school. For instance, this experimental study included sixty-eight students: thirty-five were in the experimental group and thirty-three in the control group. A pre-test and a post-test were applied, based on the Key English Test from Cambridge Exams according to the Common European Framework of Reference for Languages (CEFR). The findings revealed that the students who used the methodological guide improved their communicative competence, as confirmed by the statistical criteria of the T-student test.