Actually academic achievement is something IQ tests excel at predicting quite well. We also, on average, see clear differences in average intelligence between people with differences in academic achievement, if one was tempted to dismiss the greatest achievement of psychometrics out of hand based on this.
I don't deny that. I'm not one of those IQ-doesn't-measure-anything people.
conscientiousness isn't another thing the educational system selects for, it is the second best predictor, but it is just that, second best.
Okay, so: When you measure a correlation, you aren't just measuring how two things are related. Construct validity plays a huge role.
If you just asked people "How smart are you" and correlated it with grades, you'd likely see a positive correlation. But if you give them Raven's Progressive Matrices, you'd see a much stronger correlation with grades.
The correlation reflects not just the relationships between underlying phenomenon, but the degree to which you have successfully measured the underlying phenomenon. Unless you're measuring opinions or something, self-reports suffer from all sorts of issues with validity that cognitive tests do not.
So when you compare simple self-reported conscientiousness to IQ (which is, as you said, the greatest achievement in psycho-metrics), you're pitting a mouse against a lion.
The study I cited further down the thread, which says that willpower is more important than IQ, was able to get that result because they put a lot more effort into measuring willpower than other studies. The willpower variable was a composite of several self reports, teacher reports, parent reports, and a behavioral delay of gratification task. This composite willpower score will have more validity than any of its individual components.
(It's the same with IQ: a composite IQ test, with verbal tests, visuospatial tests, reaction time, etc will be more g-loaded (against a separate test battery,) than any individual measurement, and will probably predict grades better too. Excuse my glossing over things - see here for an example of how CCFT's low question diversity results in lower g)
Don't be too quick to downplay the importance of conscientiousness - a lot of the weaker correlations can be chalked up to the difficulty of measuring the underlying thing.
If you just asked people "How smart are you" and correlated it with grades, you'd likely see a positive correlation. But if you give them Raven's Progressive Matrices, you'd see a much stronger correlation with grades.
That's not self-evident to me, if only because people's self-perception of smartness is likely to be (partially) driven precisely by their grades.
The soon-to-be-resigning Dominic Cummings, advisor to the Education Secretary of the Coalition government, has released a 250-page manifesto describing the problems of the British educational establishment ("the blob" in Whitehall parlance) and offering solutions. I post this here because both his analysis and recommendations are likely to be interesting to LW, in particular an increased emphasis on STEM, broader knowledge of the limits of human reasoning and how they relate to managing complex systems, an appreciation for "agenty"-ness in organizational leadership, whole-brain emulation, intelligence enhancement, recursive self-improving AGI, analysis of human interactions on a firm evolutionary-psychological basis, and a rejection of fashionable pseudoscientific theories of psychology and society. Relevant extracts: