In project-based learning (PBL) courses, which are common in design and technology education, instructors regard both the process and the final product to be important. However, conducting an accurate assessment for process feedback is not an easy task because instructors of PBL courses often have to make judgments based on a limited view of group work. In this paper, we provide explanations about how in practice instructors actually exhibit cognitive biases and judgments made using incomplete information in the context of an engineering design education classroom. More specifically, we hypothesize that instructors would be susceptible to human errors that are well known in social psychology, the halo effect and the fundamental attribution error, because they have a limited view of group work when they facilitate distributed and remote groups. Through this study, we present two main contributions, namely (1) insights based on classroom data about limitations of current instructor assessment practices, (2) an illustration of using principles from social psychology as a lens for exploring important design questions for designing tools that monitor support oversight of group work. In addition to the study, we illustrate how the findings from our classroom study can be used for effective group assessments.