Digital tools can guide and support teachers in professional development programmes. The aim of this study was four-fold: (1) to explore changes introduced in classroom methodology by secondary school teachers during their participation in a professional development programme, using the digital tool EVALOE-DSS, based on conversational methodology; (2) to analyse the impact of introducing conversational methodology in the development of students' oral competence; (3) to determine the relation between students' self-perception of oral competence and self-perceived emotional competence; and (4) to find out the teachers' opinion about their experience in the programme. The instruments used were the digital tool EVALOE-DSS, the Test of Self-Perceived Oral Competence, the Self-Report of Emotional Intelligence, the Trait Meta-Mood Scale, and a satisfaction questionnaire. The study was developed in four phases: initial intensive training, intervention using the digital tool for four months, students' assessments and teachers' evaluations. The results of teachers' self-assessments using the EVALOE-DSS showed that their self-assessment of classes significantly improved throughout their participation in the programme. In addition, students whose teachers participated in the programme were self-perceived as more competent at oral language, and this had a positive influence on their self-perception of emotional competence. Finally, teachers were positive about their participation in the training process using the EVALOE-DSS. In conclusion, this study seems to suggest that a professional development programme using a Computer Assisted Language Learning (CALL) tool could provide an important strategy for increasing teachers' oral language teaching quality and improving student learning.