The purpose of this study is to evaluate the effects of a classroom long term project centred on experiences related to composting with earthworms (vermicomposting) in secondary Biology classrooms. The project aimed to systematically incorporate practical activities with living beings as situated teaching-learning scenarios in the context of predominant lecturing type teaching practices. Participants were 6 Biology teachers working in two state schools and 332 students aged 12-13 in a suburban area of Monterrey, a northern city of Mexico. Several small groups of students within each class took care of a composting bin with earthworms during a school year. This task involved feeding and dampening earthworms in the composting bin, as well as measuring and recording temperature and humidity regularly. Teachers and students engaged in activities related to nutrition, respiration, reproduction of earthworms and their role in environmental processes. Students’ productions were collected in selected sessions. At the beginning and at the end of the project, students responded to a questionnaire that explored biological knowledge, some process skills (understanding, interpretation y application of information) and environmental awareness attitudes. Students also produced free texts about what they liked and disliked in the project. These texts were qualitative analyzed. The comparison of initial and final questionnaire results suggested that students improved significantly in their biological knowledge about earthworms and composting, their ability to understand, interpret and apply related information. Students’ texts reflected evidence of high motivation to participate in vermicomposting activities, attitudes of responsibility and collaboration, and the developed of increasing interests in living beings and environmental issues.