In many countries, students are asked about their perceptions of teaching in order to make decisions about the further development of teaching practices on the basis of this feedback. The stability of this measurement of teaching quality is a prerequisite for the ability to generalize the results to other teaching situations. The present study aims to expand the extant empirical body of knowledge on the effects of situational factors on the stability of students' perceptions of teaching quality. Therefore, we investigate whether the degree of stability is moderated by three situational factors: time between assessments, subjects taught by teachers, and students' grade levels. To this end, we analyzed data from a web-based student feedback system. The study involved 497 teachers, each of whom conducted two student surveys. We examined the differential stability of student perceptions of 16 teaching constructs that were operationalized as latent correlations between aggregated student perceptions of the same teacher's teaching. Testing metric invariance indicated that student ratings provided measures of teaching constructs that were invariant across time, subjects, and grade levels. Stability was moderated to some extent by grade level but not by subjects taught nor time spacing between surveys. The results provide evidence of the extent to which situational factors may affect the stability of student perceptions of teaching constructs. The generalizability of the students' feedback results to other teaching situations is discussed.