I think it's more complicated than grades, IQ, or test scores. I know plenty of people that had mediocre or terrible grades, but had many successes in life.<p>How do you define success? ability to support yourself? Retire at 40? support children?<p>It also has to do with: drug/alcohol addiction/consumption, personal choices and life decisions (If you have children before you are married/can support them, you will most likely), and if you actually graduate from high school (grades reflect this, but you are pretty much destined to low-paying wages/jobs with no high school diploma in the US).
"Colleges and employers interested in predicting the success of applicants would do better to look at a student’s grades, which measure personality traits, like grit and attention to detail, more effectively than IQ and SAT tests"<p>High grades are a great predictor of high parent involvement and a knack for succeeding in a rigid education system. They might as well say colleges predicting long-term success should look at economic status of applicants.