Amen to the "bait and switch" thing. My property professor last semester focused ENTIRELY on policy, but come exam time, we were tested on pure Black Letter Law. He also told us not to focus on the Rule Against Perpetuities, and yet, we had 2 questions on that rule on the exam.
General rule of thumb I've found to always be true: when your professor tells you one thing, do the complete opposite...has worked for me so far!