Originally Posted by Unregistered

Grades are also an imperfect reflection of one's intelligence - it rewards the hard workers who do well in an established structure. These people also make the best junior associates given that all that is required of junior associates is the ability to execute to the letter in accordance with the partner's/senior associate's instructions. Once a lawyer gains more experience, the expectation is for said lawyer to be able to exercise critical thinking to capture the issues at hand and to define the structure for execution - this is an entirely separate skill which law school does not teach (well). Usually, this is a capability that can only be detected by partners in their associates when these associates have been with the firm for a while (at least a year).

In other words, the abilities expected of partners are different from that of a junior associate. But partners usually hire the best that they have access to anyway, since it is a roll of the dice as to whether an associate possesses partner-level potential and it is impossible to tell at the interview stage.