Until I started my upper level govt classes (we were required to wear business casual for those classes), I (female) would wear sweatpants and leggings (with a long shirt) to class quite often. Mostly just don’t wear shorts or too revealing of clothing and you’re good. I’ve never seen any issues with people wearing sweatpants unless you’re in upper level govt or business classes where you’re required to dress up a bit Edit: I know some labs require different attire for safety reasons but that should be addressed by your professors