The present work was carried out with students of compulsory secondary education. The research was prompted by the idea that scientific vocation among young people is shrinking and that this has a significant impact on our society. Consequently, a science project based on the students' interests was proposed. They were able to work as a single group and design the methodology to achieve the goal they set: 'understanding how fish function and knowing all the organs they need to live underwater'. As this objective involves considering fish within a broader system, it seems their research work inspired system thinking. Nevertheless, during the experiment session, they tried to link their comments to a traditional evaluation. Their research questions were completely conditioned by what they thought they would be assessed on under usual conditions. On this basis, they only chose to know the name of the parts and their practical uses. Therefore, although they initially considered the environment as a part to study to learn how fish function, evaluation limited their research to finalist questions. Other results, such as observation of the peer learning process, are also shown.