A study conducted by the Mathematical Association of America showed that calculus not only has significant effects on students' decision to pursue STEM fields, but also on their attitudes towards mathematics. Inspired by this large-scale study, the present study sought to deepen the current understanding of the impact of calculus on student attitudes towards mathematics. Results of an implementation of the Modeling Practices in Calculus (MPC) model, an innovative active learning in mathematics (ALM) approach, in Calculus I at a large, urban, research intensive (R1) institution are presented. Using a randomized-control trial research design, students were randomly assigned to either traditional, lecture-based classrooms, or MPC classrooms. The Attitudes Towards Mathematics Inventory (ATMI) was used to measure student attitudes at the beginning and end of the course and results were compared from both MPC and traditional sections. Overall, MPC sections showed improvement over traditional instruction by having less negative impact on student attitudes. The enjoyment and self-confidence ATMI subscales showed significant differences at course completion for both semesters, when controlling for pre-ATMI score and term. Furthermore, the MPC model had a positive impact on female students' self-confidence as opposed to male students, acting as a gender equalizer.