Early childhood educational research had shown that when children were prepared to succeed in school, they earned higher grades and learned more effectively. Children from low-income families had fewer resources than children from higher-income families to prepare them for school. Research had shown that children from low-income, minority backgrounds tested "substantially lower"[16] than middle-class children in school-related skills, and that they continued to have educational deficits throughout school.[17] The field of developmental psychology had grown during this period, and scientists were beginning to understand that changes in early childhood education could increase children's cognitive growth.