This work analyzes the educational proposals designed by 130 future secondary school teachers (FTs) to address socioecological problems--in this case, the presence of microplastics in the environment--, and the relationship with their own perceptions and commitments regarding these problems. The research design was mixed, with both qualitative and quantitative analysis of the data. Results showed that systemic thinking regarding the problems, with a comprehensive ecological but also social perception, was correlated with proposals which were aimed at promoting critical thinking and reflection among pupils. Likewise, committed FTs--who show a greater willingness to reduce their plastics consumption and who, above all, assume greater personal responsibility--tend significantly towards action-oriented approaches. Nevertheless, these approaches continue to be scarce. This leads us to discuss the need for greater emphasis on instructional practices in education for sustainability in teacher training.