Most highly intelligent people spend the majority of their K-12 schooling taking classes designed for average-intelligence people who match their chronological

Most highly intelligent people spend the majority of their K-12 schooling taking classes designed for average-intelligence people who match their chronological age. They can achieve at a given level in class with much less effort than those around them, and they generally aren't given a strong incentive to achieve more. If they develop the habit of working hard to achieve at their limits, it's probably because they have a strong interest that they pursue outside of school.