Just because your friend got a higher grade doesn't necessarily mean that he is smarter or better than you. I got a C on a college paper before, not because it deserved a C, but because the professor was/is a biased a-whole. When he found out my boss and I were good friends (he wanted to date my boss), my subjective grade suddenly increased. Also, some students know how to play the game, using big words and such, and if used correctly, sometimes professors mistake that for true knowledge.