Teaching algorithms in upper secondary education: a study of teachers' pedagogical content knowledge

Background and Context: Computing education is expanding, while the teaching of algorithms is less well studied. Objective: The aim of this study was to examine teachers' pedagogical content knowledge (PCK) for teaching algorithms. Method: We conducted semi-structured interviews with seven computer science (CS) teachers in upper secondary education (students aged 15-18). The data were analyzed qualitatively. Findings: We found two patterns of variation in teachers' PCK. First, we detected variation in the teachers' goals related to their view of algorithms: they either focused on "thinking" about the algorithm as an object, or focused on "thinking and making", where the algorithm is also regarded as a program. Second, we found variation in teachers' knowledge about responding to differences between students, which may be generic or topic-specific. Furthermore, our findings reveal that teachers consider class discussions to play a significant role as an instructional method for provoking reflection. Implications: Our findings regarding PCK may be beneficial for the development of teacher education and professionalization activities for CS teachers.