This study of first year high-school students in South Australia focussed on the effectiveness of using an innovative project-based mathematics strategy to improve the classroom learning environment and the student outcomes of enjoyment, academic efficacy and achievement. As well, we investigated the differential effectiveness of project-based mathematics for male and female students. A sample of 284 students from a co-educational private secondary school provided quantitative data about classroom learning environment as assessed with seven scales from the What Is Happening In this Class? (WIHIC), together with data about the three student outcomes assessed with one scale each. Our study also included a mixed-method design involving qualitative information collected through classroom observations and interviews with 20 students and 3 teachers to explain patterns emerging from the analysis of quantitative data.