While the grades gap between children from rich and poor families has been attributed to a variety of factors over the years, a new study shows that poor planning skills could be a major factor in the so-called income-achievement gap.

Researchers at Cornell University looked at data on around 1,500 U.S. children that were part of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. The kids were diverse in ethnicity, socioeconomic background, and geographical location. The study found that a child’s planning skill assessment in the 3rd grade could predict that same child’s classroom performance in the 5th grade, regardless of IQ scores. The research has been published in the journal Child Development.

“Low-income children appear to have more difficulty accomplishing planning tasks efficiently, and this, in turn, partially explains the income-achievement gap,” said Gary Evans, a co-author of the study and a professor of human ecology at Cornell University. “Efforts to enhance the academic performance of low-income children need to consider multiple aspects of their development, including the ability to plan in a goal-oriented manner.”

Evans and his colleagues gave multiple suggestions for why poor planning might be associated with lower income. Children with a low-income background could have greater disruptive forces in their lives, such as moving homes, moving schools, family drama, “crowded and noisy environments,” and less structure to their daily routines. Another suggestion is that low-income parents could themselves be less skilled at planning.