The American Psychologist is the flagship journal of the American Psychological Association, and the Journal of Educational Psychology is a highly respected APA journal, so these are top-notch articles. In the JEP article, Greenwald presents the results of structural equations modeling done with data from student ratings of instruction administered to 200 undergraduate classes across three consecutive terms at the University of Washington. Greenwald did evaluate other possible interpretations of the fairly strong relationship between Expected Grades and Course Evaluations. This is, by the way, the model to which I am emotionally attached. Greenwald rejects this model because it does not predict the obtained negative correlation between expected grade and how much the students work on the course.
More able students achieve more, and thus expect better grades.
This model is rejected because it anticipates none the correlations among expected grades, workload, and ratings of the course. The student who is more motivated by this course than by other courses will work more, thus achieve more and expect a better grade, leading to better ratings of the course. This model is rejected because it does not predict the obtained negative correlation between expected grade and how much the students work on the course. Given the results of much past research in attribution theory, we expect most students to take personal credit for good grades and to blame the professor for bad grades. On the other hand, if these correlations are computed within classes, all of the models except the Teaching Effectiveness model predict this correlation to be positive.