It's possible but not in large lecture courses. I took a class with <15 people and our prof was so kind as to essentially let us get in our proofs whenever (whi

It's possible but not in large lecture courses. I took a class with <15 people and our prof was so kind as to essentially let us get in our proofs whenever (which was an absolute lifesaver). But at that scale you of course can tell whether or not people are understanding without the assignments (since everyone is proving things together in class!)