This is a problem I have struggled with for years:  Chronicle of Higher Education, Professors: Hot at Their Own Risk:

Research shows that attractive people do better in life. They are treated better by teachers, doctors, even strangers, and are more likely to be hired and promoted than those who are less attractive. But in academe, being hot has a downside: Professors who are considered too good-looking can be cast by their peers as lightweights, known less for their productivity than for their pulchritude. …

Although research shows that students give better teaching evaluations to professors they think are attractive, good looks can also be a burden in the classroom.

Students have been falling in love with their professors for decades. But the professor used to be a larger-than-life figure on whom the smitten student nurtured a quiet crush. Now sites like RateMyProfessors allow undergraduates to broadcast their feelings, sometimes in the crassest terms.