Previous studies have provided insights into classroom etiquette through research focused on observing small student groups, with no significant exploration, through survey research, of classroom etiquette in a large sample. The present study addresses this gap through a questionnaire measuring students' self-perceptions of classroom etiquette. A review of empirical studies on classroom etiquette, misbehavior, and students' silent in-class behavior allowed the development of this classroom etiquette questionnaire. We then ran a series of factor analyses on 44 questionnaire items extracted from the literature in a sample of N=113 university students enrolled in the life science department of a private university in Gunma, Japan. The statistical results revealed only 22 items being relevant to the Japanese university classroom. These items fell into four underlying dimensions: Misbehaviors (rude or unwelcome behaviors), Disengagement (behaviors related to off-task activities), Apprehension (behaviors triggered by the anxiety of speaking up in class and worrying about other people's judgments), and Silent in-class behavior (the adoption of silent behavior to prevent class disruptions). Further analysis of the relationships between these four factors, using Spearman's rho correlations analysis, revealed a high degree of association between Apprehension and Silent in-class behavior and moderate, but significant, associations between Disengagement and Misbehavior, and between Disengagement and Apprehension. These relationships were further explored through in-depth interviews with ten university students of the same university. The significant findings showed that although the interviewees reported having a positive image of students who expressed personal views during class, most of them preferred to remain silent. They felt afraid of making mistakes and appearing ignorant if they made inquiries or provided incorrect answers. Silent in-class behavior plays an essential role in classroom etiquette as it prevents disruptions or the exchange of conflicting opinions during class while preserving harmony in the classroom, and at the same time, is used as a face-saving action by students to prevent damage to their self-esteem. This study contributes to the body of research on classroom etiquette by supporting the findings of previous qualitative studies. It also contributes by furnishing an acceptably reliable instrument that provides an initial approximation of the spectrum of student behavior within Japanese university classroom parameters.