Enabling students to evaluate the impacts of computing, both positive and negative, on their own lives and on society is an internationally proclaimed goal of a K-12 computing education. While recent years have seen the development of competency models for several areas of computing education, no model yet exists for the evaluation of computing impacts. As such, it is unclear what prerequisites students actually need to fulfil in order to competently carry out such evaluations. This work-in-progress paper describes the rationale for and methods employed in a grounded theory study to describe and explicate the nature of such evaluation processes. Based on initial interview data, first insights are presented and challenges for future work are discussed.