Are grades basically iq scores?

Explanation:

Kids with higher IQs do still get higher grades, but its predictive power is lower--the data are more scattered. A kid with higher self-discipline is a lot more likely to have a higher gpa than a kid with low self-discipline, than a kid with a high IQ is to have grades higher than a low IQ kid.

recommended becuase why did he read the book? becuase it was recommended