This should be obvious, but nothing wrong with studying the obvious:
In a study examining the links between looks and college course ratings, two researchers at the University of Texas found classes conducted by attractive professors were more likely to win top marks from students… Hamermesh and Parker say the biggest question arising from their research is whether students are discriminating against less-attractive professors or whether they actually learn less from them.
This goes along with some work one of our grad students (Boris Hellman) has done regarding perceived status. If your students think you are rich, attractive, and well-dressed, they think you are a better teacher, and they learn more.
Clearly, the university needs to start paying for plastic surgery and aesthetic coaches. Heck, shouldn’t we be getting head-shots with our applicants for tenure track positions? Perhaps we should extend this to Ph.D. students as well: we need your transcripts, writing sample, grades, recs, and a short video demonstrating your beauty and grace.