There is a wide recognition that reasoning abstractly, constructing arguments, or critiquing arguments should be an important educational goal in the mathematical experiences of all students in the standards for school mathematics. Seeing these standards as an essential element for developing deep mathematical understanding; however, call for a strong knowledge of proof for teachers. Thus, the purpose of this study is to investigate how pre-service middle school teachers (PSMTs) decide whether a presented mathematical statement is true or false and how they verify student arguments presented for these statements. 50 PSMTs participated in the study. Individual interviews were conducted with 7 PSMTs to further delve into the verification processes of the PSMTs. The results of the study demonstrated that meeting the expectations of the current standards is not an easy feat by documenting that most of the PSMTs struggled with evaluating mathematical tasks and constructing arguments.