General IQ is useful for determining how children should be treated/placed in school. For adults, it's a game. Multiple intelligences, at least, helps you make career choices.
Which...is good and bad, IMO. Because kids know when they're being singled out, and they feel that they're either "smart" or "dumb" compared to what classes they're taking. And sometimes that qualification isn't fair (nor is the pressure!). Sometimes kids just want to be kids, and they want to be in the classes where their friends are.
Obviously, I'm not a proponent of labeling kids or placement of kids based on their IQs. I think there are better ways, and in fact I think some of the kids labeled as "slower" may just be bored and need higher level courses to stimulate them. Some of them take IQ tests and do poorly on parts because they honestly don't get the questions - not because they're too dumb, but because the question doesn't match with their perception of the world.
I'm really just saying that we can't use IQ to determine placement of a child that may influence them for the rest of their lives. I've seen too many even at the college level crash and burn because of this magical IQ, which was supposed to make everything go well for them.
I still say all students should be in the same classroom, but there should be more peer counseling. If the student is smart enough, then they should be teaching their peers what they know. Even at the grade school level.
But meh. Really, I'm not slamming anyone for their opinions. I'm just saying we shouldn't use IQ as the "end all/be all" label for intelligence or intelligent people. Arts, music, literature, and debate/social skills should be just as valid qualifiers for intelligence markers.