This study examined parent and youth self-reports to test the hypothesis that perceived insufficient sleep duration, inconsistent sleep habits, reduced quality of life, less frequent blood glucose monitoring, and higher hemoglobin A1c would predict poorer school functioning among 50 youth with type 1 diabetes. The data suggested that a delay in bedtime on non-school nights compared with school nights was consistently related to lower grade point averages and lower reading, math, and writing test scores. Sleep duration on school nights related to writing performance and absences. Perceived disease burden predicted grade point averages and absences. These findings support the need for school psychologists to target sleep problems and quality of life in youth with diabetes as a way to help improve their school performance.