This phenomenographic study opens the classroom door to investigate teachers' experiences of students learning difficult computing topics. Three distinct themes are identified and analysed. "Why" do students succeed or fail to learn these concepts? "What" actions do teachers perceive will ameliorate the difficulties facing…

"Threshold concepts" are concepts that, among other things, transform the way a student looks at a discipline. Although the term "threshold" might suggest that the transformation occurs at a specific point in time, an "aha" moment, it seems more common (at least in computing) that a longer time period is required.…