Since the introduction of systems thinking inventory tasks or “Bathtub Dynamics” tasks in 2000, an increasing number of researchers and educators have confronted various student groups and post-graduates with these tests to assess and evaluate their understanding of basic system thinking skills and system concepts. Surprisingly, the results showed a poor performance. This motivated us to subjecting students in Germany to the Bathtub Dynamics tests so as to broaden the international research data and to gain a better understanding of the current level of system thinking skills in selected student groups at our educational institutions. Three different groups, two at university and one at high school level, received the same tasks. The performance results were compared to each other and to other research studies that applied the same tests. The task results were assessed to discover any correlation with the subject’s demographics, such as age, gender, previous degrees or university courses. As was shown with other studies, the overall performance was poor given the participants’ education level. The interesting aspects are the specific differences in performance between and within the individual groups and the relationship to demographic factor such as gender.