The test taking ability is highly correlated to real world ability on practical tasks. See, for example, Hunter and Schmidt, “The validity and utility of select

The test taking ability is highly correlated to real world ability on practical tasks. See, for example, Hunter and Schmidt, “The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings.” (1998), which summarizes a mountain of research over almost a century, and in fact finds that test taking ability is strongly predictive of real world performance.