Building on previous studies on action-oriented strategies for teaching race-related courses, we explore the general effectiveness of teaching about racial stereotypes and racial/ethnic identity construction in two undergraduate race and ethnicity courses. Given that race and the term "White" are culturally constructed and serve to maintain racial power in the U.S., this study focused on student conceptions of the categorization of whiteness. Specifically, we ask to what degree students' general perceptions of race, their confidence in identifying the percentage of Whites or non-Whites from a list of twenty-seven countries, can change after exercises in critical thinking and active learning. We found that students' generalized perceptions of people from other countries were in fact radically different after going through the lessons and projects. Students who received the materials were less confident in who was White or not and thus overwhelmingly answered that they were "not sure" when prompted to classify the racial/ethnic backgrounds of each of the twenty-seven different national groups.