The pervasive income–achievement gap has been attributed in part to deficiencies in executive functioning (EF). The development of EF is related to children's planning ability, an aspect of development that has received little attention. Longitudinal data from the National Institute of Child Health and Human Development study of early child care show that early childhood poverty (1 and 24 months) is significantly related to fifth grade, math, and reading achievement (n = 1,009). The ability to plan in Grade 3, indexed by the Tower of Hanoi task, mediates the income–achievement gap in math and to a lesser extent in reading. IQ was incorporated as a statistical control throughout.