Background: Research shows that active pedagogies could play an important role in achieving more equitable outcomes for diverse groups of students in Science, Technology, Engineering, and Mathematics (STEM). Although flipped classes are a popular active methodology, there is a lack of high-quality studies assessing their impact in ecologically valid settings and exploring how outcomes are related to gender and to prior education. Purpose: This paper presents two modified replications of an experimental study investigating the impact of the flipped class approach on students' achievement in a large, first-year class in an engineering bachelor's degree. Methodology: We added a new strand, progressively flipped over 3 years, to eight parallel strands of a high-stakes mandatory linear algebra course for engineers. The study followed a replicated-between-subjects design, with students in the flipped strand learning the same material as those in the other strands and taking the same final exam. Results: Our results demonstrate that the flipped format did not have any significant impact on students' achievement compared to traditional lecturing. However, both replications in the flipped condition show a reduced attainment gap for women and students with less prior knowledge in mathematics. Conclusion: While the flipped class seems to have weaker effects on learning than other active methodologies, the evidence in this study indicates that it may have an impact on reducing the attainment gap between different groups of students. It may therefore be particularly interesting to consider in efforts to achieve more equitable outcomes for women and where students have heterogeneous educational backgrounds.