The object of the study is teaching students majoring in information technology to create use case diagrams with a high level of detail during the period from 2016–2017 to 2023–2024 academic years. The research is motivated by the need to improve the quality of information system modeling and eliminate defects in use case diagrams, which is critical for the professional training of IT specialists. The methodology includes the development of a teaching technique for creating use case diagrams and its testing with the categorization of defect types and analysis of their prevalence. The study is based on an analysis of 438 graphical models containing 6060 identified defects. We have developed a teaching technique of model creation that includes a two-dimensional typology of defects.  The first dimension is the models quality, for which criteria are considered at the top layer: completeness, redundancy, and correctness. We proposed a second dimension of defect severity: critical, major, minor defects.  An increase in the effectiveness of model creation training using the developed technique is demonstrated. The defect number in the use case diagrams (UCD) is practiced as an indicator of training objectives achievement. The defects are of a sustainable nature, while their density depends on the modeling mode and the didactic materials used. The proposed methodology can be applied to other types of diagrams when teaching information systems modeling.