She analyzed data from the National Longitudinal Study of Adolescent Health – a nationally representative study of 20,000 adolescents in grades 7 through 12 interviewed in 1995; follow-up interviews were conducted a year later with 14,000 of the participants. That national study was designed by J. Richard Udry, Peter S. Bearman and Kathleen Mullan Harris with a grant from the National Institute of Child Health and Human Development and cooperative funding from 17 other agencies.
Heard examined four types of family and parental resources that might help explain the relationship between family structure and adolescent educational achievement: economic resources, parental social control, parents' conveyance of their educational expectations to their children, and family stress created by frequent moving.
"My goal was to consider inequality in family and parental resources as possible mechanisms that explain the negative effects of non-intact family structure on three measures of adolescents' interest in school: grade point average, college expectations and school discipline," Heard said. "The results show that the level of economic resources within families had a strong and positive relationship with all three school outcomes and consistently explained the deficits faced by children living with single mothers."
Adolescents living with both biological or adoptive parents have the highest grades, are more likely to have high expectations of going to college and are least likely to have been suspended or expelled from school. In contrast, adolescents living with single fathers and with nonbiological parents/relatives have the lowest levels of academic achievement, are least likely to have high expectations of attending college and are most likely to have faced school discipline.
Single-mother families and nonbiological parent families are most likely to have incomes that fall below the poverty line for a family of four. The economic deprivation faced by adolescents with single mothers accounts for their educational disadvantage. "Single mothers may not feel that they have the financial resources to pay for their adolescent's education and thus do not make as strong of an effort to encourage their children to attend college," Heard said. "However, it is also possible that, despite their economic deprivation, single mothers who do hope their children will receive a college education are less able to convey that goal to their children effectively." The overwhelming responsibilities felt by many single mothers might also hinder their ability to plan beyond the immediate future.
"Economic deprivation is the most detrimental consequence of growing up with a single mother," Heard said. She suggested income-transfer programs, such as child-support enforcement, and education and job-training programs that help single mothers earn higher wages might alleviate some of the negative educational consequences for adolescents living with single mothers.