The purpose of this study was to examine the relationship between teaching quality and students' harmonious passion, deep strategy to learn, and epistemic curiosity in mathematics in 1,003 high school students. Data were analyzed using multilevel structural equation modeling, and results showed support for the hypotheses tested. First, we found that teaching quality -- specifically, providing an optimal challenge, focusing on the process, and offering positive feedback -- predicted students' harmonious passion. Second, students' harmonious passion predicted, at the individual and class level, students' deep strategy to learn. Third, students' harmonious passion predicted, at the individual and class level, students' epistemic curiosity. Findings were discussed regarding their implications for educational practice and methodological suggestions for future research.