Traditional Software Engineering courses commonly prioritize the teaching of methodologies and concepts in small and controlled environments. This decision is partly justified by the difficulty of bringing real software projects to the classroom. The ubiquity of Open Source Software (OSS) projects contributes to mitigating this problem. Several instructors already make use of contribution to OSS as part of the teaching and evaluation process in their courses. However, little is known about how students perceive the approach of contributing to OSS projects in the context of a Software Engineering course. This paper aims to uncover challenges and benefits from the students' perspective. To achieve this, we conducted14 semi-structured interviews with students who attended to this kind of courses in five different Brazilian universities, resulting in findings not so well known. For example, we noticed that, although instructors point to the projects that students are required to contribute to, students (and the project community) are involved in the process of choosing projects and tasks (issues). We also identified that students' contributions vary in terms of number of lines added and removed in commits, as well as the use of different programming languages.