Although a number of studies report about novices’ diffi-culties with basic flow-control constructs, concerning both the under-standing of the underlying notional machine and the logical connectionswith the application domain, this issues have not yet been extensivelyexplored in the context of high-school education. As part of a projectwhose long-run goal is identifying methodological tools to improve thelearning of iteration, we analyzed how a sample of 164 high-school stu-dents’ approached three small programming tasks involving basic loopingconstructs, as well as two questions on their subjective perception of dif-ficulty. If, on the one hand, most students seem to have developed aviable mental model of the basic workings of the underlying machine,on the other, dealing at a more abstract level with loop conditions andnested flow-control structures appears to be challenging. As to the impli-cations for teachers, the results of the analysis suggest that more effortsshould be addressed to develop a method for testing the conjecturesabout program behavior, as well as to the treatment of loop conditionsin connection with the problem statement.
