Critical education scholars contend that schools ought to play a role in the transformation of inequitable institutions and social arrangements. In part, this entails educating students in the academic disciplines, viewed as powerful lenses through which students might see the world in order to better understand why things are the way they are and how they might be different. Using a critical theoretical perspective on mathematics literacy, this study examined high school students' views of mathematics in light of their experiences with mathematical investigations of social problems. Qualitative research methods were used in data collection and analysis. Data were gathered in a statistics class and a mathematical modeling class during fifty days of classroom observations, interviews with sixty students and two teachers, and a review of student work. Spradley's analytic techniques, known as domain analysis, were used to identify themes in the data. Students in this study indicated that their classroom experiences caused them to rethink their ideas about mathematics. They described mathematics as an indispensable tool for disclosing social injustices. Some students stated that prior to their investigations they took equality in the US for granted. Even students who suspected biases in social practices had not figured on the subtle form they sometimes take. At the same time, they indicated that applying mathematics to social problems is not unambiguous, unproblematic, and as objective as they had previously thought. As a result, applications should be scrutinized with respect to their assumptions, methods, and conclusions. Critical mathematics education scholars argue that students will construct views of mathematics and society that are less mystified if they experience the use of mathematics as a tool for social critique in the classroom. This study supports their argument.