Low grades, bad behavior? Siblings may be to blame, FSU study says

On average, adolescents living with half- or stepsiblings have lower grades and more school-related behavior problems, and these problems may not improve over time, according to Florida State University Assistant Professor of Sociology Kathryn Harker Tillman.

“These findings imply that family formation patterns that bring together children who have different sets of biological parents may not be in the best interests of the children involved,” Tillman said. “Yet one-half of all American stepfamilies include children from previous relationships of both partners, and the majority of parents in stepfamilies go on to have additional children together.”

Many studies have focused on the structure of parent-child relations in connection to academic achievement, but Tillman’s study is unique in that it focuses on the composition of the entire family unit. Tillman studied data from the National Longitudinal Study of Adolescent Health, a nationally representative study of more than 11,000 adolescents in grades 7 through 12 in the United States. Her study is published in the journal Social Science Research.

All stepfamilies are not equal -- at least in terms of their impact on children’s academic performance. Surprisingly, teens who live in the most seemingly complicated family arrangement of all -- those with both half- and stepsiblings fare better than those who live with only stepsiblings or only half-siblings. Tillman theorized that perhaps the decision of the parents in these families to have a biological child together reflects a stable relationship or one in which child rearing is especially important. Only 1 percent of youth in Tillman’s study lived in this so-called complex blended sibling composition, however.

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