This longitudinal study was designed to examine how science, technology, engineering, and mathematics (STEM) project-based learning (PBL) affected the success of high school women in comparison with high school men in mathematics and science, with English performance as a control. We analysed the four-year performance, course-taking, and retention of high school students (n= 186) in these three subjects in a school where STEM PBL was enacted. Students’ Texas state-mandated high-stakes test scores were collected. A repeated measures MANOVA was used for analysing changes in performance after infusing STEM PBL activities into their classes. The results indicated that there was a statistically significant change in scores for both men and women in mathematics and science; however, the attrition for women was much less than for men. We included implications for how to escalate women's performance and retention in STEM-based areas.