Orin Kerr has done 1Ls around the country a great service by writing a very clear guide to distinguishing between Bad Answers, Good Answers, and Terrific Answers to 1L exams.
While the principles also have considerable applicability to more advanced courses, I think that we professors legitimately expect all this and more from 2Ls and 3Ls, including more complex issue-spotting, coping with more complex and contradictory rules, and taking account of various sorts of policy considerations (when relevant), to name just three. Actually, might we hope for some of those in the terrific 1L answers too? I should admit here that it's been far too long since I actually taught first years, and for some to-me-incomprehensible reason the day students (but, it must be said, not the students in our since-dismantled night program) said I was too scary….
Update: on the subject of exams, Paul Ohm has a thoughtful post about achieving fair grading in a common grading situation. (Personally, I grade each question separately and average them, but that's not without issues.)