This paper describes and problematizes the pedagogical practices developed by a trainee in initial formation with three first grade high school classes in a public school in Porto Alegre, Rio Grande do Sul, Brazil, in the second semester of 2017. This is a qualitative exploratory study based on documentary source (the report produced at the end of this formative period). In this article the focus is on classroom activities that have as a reference the methodological approach called problem-based learning, as well as the assessment and self-assessment activities that were proposed by the teacher and performed by high school students. The teacher in formation centrally addressed some conceptual content related to Inorganic Chemistry with the adoption of the theme "pollution" as a way to try to connect the discussions held with the students' daily life. The systematized results which were discussed in this article indicate that important elements of learning about the teaching work were constituted favoring the effective development of the intern that was investigated. The latter was able to take a safe position on his work which includes, especially, evaluation processes that unveiled factors concerning student learning and the methodological choices adopted in the process.
