For many gifted students, the school day is a snooze-fest. Seven in 10 public school teachers agree that “too often, the brightest students are bored and under-challenged in school,” according to a 2008 study from the Thomas B. Fordham Institute.

The problem? Most schools force teachers to adhere to a single lesson plan designed for the median student. When teachers deviate from their lesson plans, it is usually to make content more accessible for students who are underperforming. Gifted students complete their assignments...