Cyrus said:
All my professors wear professional attire. Some wear suits, every day. Never once has any of my professors wore a t-shirt. Ever. ~50% wear a tie with dress pants but no blazzer.
Who teaches a class in a t-shirt? Get real.
Well, I did know one crazy old professor who taught in sweatpants, but that's what happens when you teach in sweatpants, you get a reputation for being a "crazy" old professor. Actually, since the sweatpants were often red, and he had a full, white beard, he looked a lot like Papa Smurf.
I wear jeans when I have to go to work on weekends, but never to teach. Considering the faculty have to arrive to work before students show up to classes (even if we walk into the classroom after you, we've been in our office preparing beforehand), and we manage to dress professionally, there's no reason for the students to be showing up in whatever they wore to bed the night before. To show up in your pajamas, or what could be pajamas (i.e., sweatpants), gives off a pretty anti-social vibe...sort of the "I don't give a darn what you think, leave me alone in my own world" message. Jeans are fine if they aren't ripped, and even a newer t-shirt is okay, just not the old, faded, stained, torn t-shirt you've had since junior high. You can look decent and blend in. If you want to stand out from the crowd, and give off the vibe of "I'm really confident and am not afraid to be noticed," then dress nicer than just the usual jeans and t-shirt look every other college student wears.
The thing is that once people get to know you, jeans, t-shirts, etc., are all fine and won't change their opinion of you, but before they have gotten to know you, your appearance is the only first impression you can make. If you look more "put together" people will assume you do have your act together. You don't want to go to the other extreme of looking like a clown either, because then people will notice you but not take you seriously at all.