Actually, I once wore depends (back when they were still half-decent) to a college class. One other student just happened to notice the diaper bulge, and started taunting me for it. The professor eventually stopped his class to find out what the commotion was all about, and I got outed to the whole class.
Worse yet, I was called up to the front to explain why, and as I got up everyone noticed I had leaked a little. Not only was I completely humiliated, but I got sent to the deans office for being a dirty pedophile. The cops were called in, and I was arrested for wearing a wet diaper. My parents then found out, and I was disowned right there on the spot.
Said NOBODY! Seriously though, these kind of fears are completely unwarranted, and totally baseless. Just wear the diaper to class. Nobody notices, and even fewer will care should you actually try to make it obvious enough for them to notice.