There is no "expectation" it's all about the class and professor. My 1L Civ. Pro. class the prof. told us that if someone got 50-55% of the points, they would be the "A." There are classes where the exams are extremely difficult (they have to be to force a cruve with a larger class). Therefore, expect to walk out of some exams feeling like you failed only to find out you received a B+/A- or sometimes even that coveted "A."Welcome to law school.
I guess its not that uncommon then, I still am used to the undergrad idea of 75% being a looser who was high in the bathroom during half the test.
Its absolutely all about the professor and the class. In my civ pro class you had to get over 90% of the issues on the exam to get an A-. This was because my prof has published a series of commercial supplements which show you how to write exams that he wants. Consequently everyone who is responsible buys the supplement and thus everyone writes identical essays. Frustrating.