This comprehensive study involved the use of the what is happening in this class? (WIHIC) questionnaire among 2310 Singaporean Grade 10 students (aged 15 years) in 75 geography and mathematics classes in 38 schools. A seven-scale factor structure was strongly supported and the alpha reliability of each scale was high. An investigation of associations between classroom environment and several student outcomes revealed that better examination scores were found in classrooms with more student cohesiveness, whereas self-esteem and attitudes were more favourable in classrooms with more teacher support, task orientation and equity. Differences between the classroom environments of geography and mathematics classes were small relative to the large differences between students' actual and preferred classroom environments. (Contains 3 tables.)