Underachievers are frustrating for any teacher; these kids have incredible potential and may even be identified as gifted, but they don't do the work, won't do the work, or do the work with much less quality than they are capable of producing.
Davidson Academy: Underachievement in Gifted Students
Davidson Institute: The underachievement of gifted students: What do we know and where do we go?
Gifted Guru: How to Keep Gifted Kids Motivated
Renzulli Center: Making a Difference
What more? Take my Underachiever Course for 6 additional Gifted PD Hours: The Underachiever