Understanding how students' prior knowledge affects their learning of new concepts is essential for effective teaching. The same learning activity, or the same explanation, may have very different effects on students with different prior knowledge.
In the context of teaching programming, prior knowledge includes the programming languages students studied in prior courses. In this experience report we describe our observations in teaching object-oriented programming in Java to students who previously learned functional programming in Racket's student languages. We highlight four concrete problems we encountered in teaching the second course in this sequence. We detected and addressed these problems primarily thanks to a teaching assistant who assisted in both of the courses.
This experience made us realize the importance of explicitly bridging between languages in introductory programming course sequences. It also showed that the sharing of teaching staff across courses can be an effective way to detect aspects that need bridging.
