Hear Hear! And all learning is done on one's own, really.
IQ is, not to put too fine a point on it, bunk.
Grades are also bunk. They can never measure depth of knowledge, which is the thing that matters, intellectually speaking. Depth depends on connections formed with other areas of knowledge, which are unique to each student.
There is intrinsic to the academic system a pervasive issue of trust.
Grades can indicate the depth of knowledge, but with the disclaimer that both the arbitrating grader is trusted (in a very special sense), and that the method used to decide grades be both defensible and explicable to others.
To provide a concrete example. A paper on the first book of Hume's Treatise of Human Nature attempts to bring a new argument to bear on the consequences to modern epistemology incurred by Hume's concept of abstract ideas. The paper is written as a final in a graduate level philosophy class, and the instructor is known to be knowledgeable, intelligent, fair, and honest. The paper receives a B+. It is arguable that the mark is generally reflective of the student's understanding and ability at the time the student wrote the paper. (this example is taken from personal experience - I wrote this paper, and I feel that the grade was reflective of my knowledge on the topic)
But without the trustworthy instructor, the grade would be meaningless. The problem, if I were to speculate, is one of numbers - too many students, too few professors. A basic premise of security is that the more parties involved in a pact, the lest reliable the pact is, and if grades are to be a faithfully representation of a students ability, the reliability of the academic pact is paramount.