How do high grades constitute higher IQs? (Score 1)

I know a few people who take a few honors classes at my high school, and get pretty high grades altogether. Does that make them smart? No, actually, these people are, well, not the brightest kids on the block to put it nicely. As another example, many people tell me I'm an intelligent person, yet most of my grades around a C level, and I take all Standard classes. How much you succeed in public school doesn't have that much to do with your intelligence. I'm more convinced it has to do with how content you are with the school system, and how conveniently the work load fits into your schedule.