From the report:

In 2010, 15.5 million poor Americans were children under the age of 18 — 21 percent of all children. Poverty is a major risk factor for children’s development. Poverty in childhood, especially deep poverty, is linked to a range of physical-biological, cognitive-academic, and social-emotional problems, and these problems persist into adulthood. The Society for Research in Child Development created a policy brief on the subject. Find it at the link below.