Yes, exactly. I remember being accepted by one of Canada’s finest universities, where I, and my classmates were told, “You may have been top of your high school class to get accepted here, but now you’re competing against everybody who was also top of their high school class.” And many didn’t make it, choosing to drop out, or just plain failing.
I heard the same thing when I was accepted at law school: “You may have been top of your undergrad class to get accepted here, but now you’re competing against everybody who was also top of their undergrad class.” And the same thing happened–no matter how well you did in your undergrad was not necessarily indicative of how well you would do at law school. Accordingly, we had about 10% of our class drop out or flunk out.
No matter how smart you are or how well you did before, a new school and/or new environment with your peers means a whole new leveling of the pack. You’re no longer the smartest in the class; you’re just another student.