A number of studies report about students’ difficulties with basic flow-control constructs, and specifically with iteration. Although such issues are less explored in the context of pre-tertiary education, this seems to be especially the case for high-school programming learning, where the difficulties concern both the “mechanical” features of the notional machine as well as the logical aspects connected with the constructs, ranging from the implications of loop conditions to a more abstract grasp of the underlying algorithms. As part of a project whose long-run goal is identifying methodological tools to improve the learning of iteration constructs, we interviewed 20 experienced upper secondary teachers of introductory programming in different kinds of schools from a large area in the North-East of Italy. In addition, a sample of 164 students from the same schools answered a survey which included both questions on their subjective perception of difficulty and simple tasks probing their understanding of iteration. The interviews were mainly aimed at ascertaining teachers’ beliefs about major sources of issues for basic programming concepts and their approach to the teaching and learning of iteration constructs. Each interview was conducted according to a grid of 20 questions, informed by related frameworks to characterize teachers’ pedagogical content knowledge and to design concept inventories. In essence, data from teachers and students confirm that iteration is a central programming concept and indicate that the treatment of conditions and nested constructs are major sources of students’ difficulties with iteration.
