Many people think of gifted students as always excelling in classes but that is not always the case. Gifted student often do not perform up to the expectations given to them by being in the gifted program. There are many possible reasons why gifted students may not perform well in school:
They may not feel they can live up to the label and intentionally don't perform as well.
They might simply think differently than other students.
They might not have the motivation to do well.
They may not care about school.
They may not have the skills to succeed in an academic environment.
Definitions and causes defined (a little dull but interesting)
5 ways to tackle from someone who struggled with it
Characteristics of gifted underachievement
Stigmas of being gifted
Sorry most are for parents or teachers but you'll get the idea of how to help yourself with these resources
Books that can help you and your parents
Types based on type of underachievement