Students' creativity is a fundamental goal in education. The school has a strategic role in developing students' creativity. This study elaborates on classroom activities to develop students' creativity. The study used a mixed-method sequential explanatory design. Quantitative data were obtained from six hundred junior and senior high school students in East Java, Indonesia. Qualitative data were obtained from nine teachers. Descriptive and regression analysis techniques are used to analyse quantitative data, while thematic analysis is used to analyse qualitative data. The results show that classroom climate, especially the following classroom activities: rule, positive teaching, teacher support, and teacher classroom management, strongly affect students' creativity.