I have dropped classes during my school's drop/add period in the first week of the semester. First semester freshman year, I dropped general psychology as a night class, then ended up taking it in the spring anyway, this time as an afternoon class. I also dropped World Regional geography before classes even started, which we can do.
This year I dropped Natural Disasters because the professor gave us a homework sheet that involved calculus (!!!!) in a 100 level class. I was just like screw this; I'm not doing calc in a 100 level if I don't need to, then I dropped out. Plus he hadn't taught in five years. BIG red flag. Then this semester I had to withdraw from The Planets because I was failing no matter how hard I tried. Now I'm behind in my sciences. I just hate science/math.