The use of student evaluations of teaching performance has been an important but controversial tool in the improvement of teaching quality during the past few decades. Although student evaluations of teaching are implemented in many faculties, not everyone is convinced of the desirability and utility of these ratings. In this paper, we present the results of a study with regard to the existence of a higher-order factor that might influence students' perceptions of teaching and, thus, explain the variance in teacher rating scales. A second question concerns the effect of students' grades on teacher ratings and of other factors influencing this relationship (for instance, students' overall grades). (Contains 5 tables.)