Children of color are more likely to have poor sleep health than White children, placing them at risk for behavioral problems in the classroom and lower academic performance. Few studies, however, have utilized standardized measures of both classroom behavior and achievement. This study examined whether children's sleep (parent and teacher report) in first grade concurrently related to independent observations of classroom behavior and longitudinally predicted achievement test scores in second grade in a sample of primarily Black (86%) children (n = 572; age = 6.8) living in historically disinvested neighborhoods. Higher teacher-reported child sleepiness was associated with lower adaptive behaviors and higher problem behaviors in the classroom, and predicted lower achievement. Parent-reported bedtime resistance and disordered breathing also predicted lower achievement.