Resumo. ABSTRACT A lack of interest in physical education classes has been observed in the final years of elementary school. Studies conducted in the last decade on motivation in the discipline report a close relationship between the satisfaction of basic psychological needs and increased participation in physical education classes. This study investigated the motivational aspects that underlie the withdrawal of ninth-grade students from physical education classes. The study adopted a sequential mixed method in which quantitative descriptive and qualitative interpretive analyses were performed. In the extensive phase, the sample was composed of 85 ninth-grade students from municipal schools in Rio de Janeiro; of these, six students were selected for the intensive phase. The Basic Psychological Needs Questionnaire, adapted to Portuguese, was used for quantitative analysis and interviews were held using the dialectic hermeneutic circle technique for qualitative analysis. The results indicate a lack of ability (competence), lack of content diversification (competence/autonomy), and lack of opportunities for participation in decisions-making during development of the discipline (autonomy) as the main reasons for students’ disinterest in physical education classes at the end of elementary school.