What's worse, many of their professors—my colleagues—weren't dressed much better.
I was reminded of a wedding we attended a few years ago. The bride and groom were dressed appropriately for the occasion, as were their parents and a few fuddy-duddies. But the rest of the congregation looked as if they had just awakened in the gutter after a hard night of partying. I thought they showed great disrespect for the couple.
If you cannot afford a nice suit for your friend's wedding (or to teach your class), at least make sure your clothing is clean and mended. (A shower and a shave are usually a good idea too.)
I wear jeans and baseball caps when that style of dress is appropriate to the setting. I do not dress that way when lecturing, or when attending church, weddings, or funerals.
Well put.
Your manner of dress expresses both your feelings about yourself and the occasion or setting.