i think with studying a subject there is one more factor which plays a huge role in your level of achievement, which is your Interest toward the subject.
even if you are reletively intelligent, you cannot study if you have no interest and therefore no intention to revise.
however, even if you are'nt the brightest lot in your class, if you like the subject, and you ask questions in the class, and actually have fun revising, you would find that more information gets "accepted" into the brain.
what do you think? I believe in teachers who are interested in the subject more than teachers with incredible intelligence....