A Scratch Challenge: Middle School Students Working with Variables, Lists and Procedures

With the “Lehrplan 21” school curriculum, a new subject “Media and Computer Science” was introduced in the German-speaking cantons of Switzerland. The curriculum defines competence areas that should be achieved by students within this subject. One such competence area is that middle school students should be able to develop executable and correct computer programs that use variables and subprograms. To evaluate and analyze how middle school students work with these more abstract CS concepts, we organized a Scratch Challenge – an online programming competition using the block-based programming language Scratch. We then compared the 203 submitted projects with an analysis of projects from the general Scratch repository. We found a similar use of types and quantities of blocks per projects (when considering projects developed in a short timeframe), but also an increased use of the targeted abstract concepts (especially of procedures), potentially influenced by the educational materials we provided for the challenge. Secondly, we examined the way middle school students work with these abstract concepts in Scratch, the errors they typically make, which challenges they face and the preconceptions they might have. These results contribute to the little studied area of middle school students working with more abstract concepts, such as variables, lists and procedures in Scratch. With this contribution, we hope to support schools to implement the aims of the “Lehrplan 21” successfully, and at the same time gain insight into the use of Scratch for teaching and learning more advanced CS concepts.