This study utilised the "What Is Happening In this Class" (WIHIC) questionnaire to examine factors that influence Californian students' perceptions of their learning environment. Data were collected from 665 USA middle school science students in 11 Californian schools. Several background variables, such as gender, socioeconomic status, ethnicity, and class size, were included in the study. A hierarchical analysis of variance was conducted. Results from this study indicate that some scales of the WIHIC are more inclined to measure personal or idiosyncratic features of student perceptions and other class features. A variable that consistently affected students' perceptions was student gender. Generally speaking, girls perceived their learning environment more positively than did boys.