A growing body of research has recognized the importance of students' having active roles in feedback processes. Feedback literacy refers to students' understandings of and participation in feedback processes, and research on students' feedback literacy has so far focused on higher education; secondary schools have not received attention. This case study investigates secondary students' feedback literacy and its development in the context of formative peer assessment. From various data sources, three categories of students' feedback literacy were identified, and criteria for the levels of literacy in each category were created. The criteria were used in the coding of seventh- and eighth-grade students' skills. The results show that students were able to develop their feedback literacy skills. Thus, secondary school students should be introduced to feedback literacy via, for example, formative peer assessment.