This 3-year study compared characteristics of high ability students who were identified as high achievers with students of similar ability who underachieved in school. The 35 students attended a large urban high school comprised of 60 percent Puerto Rican students, 20 percent African American, and the remainder White, Asian, and other. Qualitative methods were used to examine the perceptions of students, teachers, staff, and administrators concerning academic achievement. The study found that achievement and underachievement are not disparate concepts, since many students who underachieved had previously achieved at high levels and some generally high achieving students experienced periods of underachievement. A network of high achieving friends was characteristic of achieving students. No relationships were found between poverty and underachievement, between parental divorce and underachievement, or between family size and underachievement. Successful students supported the concept of grouping in honors and advanced classes, had supportive adults in their lives, and participated in multiple extracurricular activities. High achieving females usually chose not to date. High achieving students characteristically had a strong belief in self and resilience to negative factors. Cultural and gender differences were also found. Case studies of the 35 students are included. (Contains approximately 250 references.) (DB)