--- - |2 This study examines how student perceptions of teacher practices contribute to female high school students’ math beliefs and achievement. Guided by the expectancy–value framework, we hypothesized that students’ motivation beliefs and achievement outcomes in mathematics are fostered by teachers’ emphasis on the relevance of mathematics and constrained by gender‐based differential treatment. To examine these questions, structural equation modeling was applied to a longitudinal panel of 518 female students from the Maryland Adolescent Development in Context Study. While controlling for prior achievement and race, gendered differential treatment was negatively associated with math beliefs and achievement, whereas relevant math instruction was positively associated with these outcomes. These findings suggest inroads that may foster positive math motivational beliefs and achievement among young women. - Journal of Research on Adolescence, EarlyView.