I don't know how much this applies to other institutions, but speaking personally, my undergrad Operating Systems course very much threw the students to the wolves.It wasn't one of those "memorize the textbook and you'll be fine" type of classes. It was a "do a bunch of independent research and figure a whole lot of things out for yourself" type of class. Logical programming (prolog).I'm not sure I would call it the most challenging class, but it's the one where the most amount of people failed ...