Stanford University sociologist Michael Rosenfeld used census data from 2000 and found nearly 7 percent of children raised by heterosexual married couples were held back a grade and about 9.5 percent of children living with same-sex partners repeated a grade.
However, the difference between the two groups of parents disappears after factoring in that the heterosexual couples were slightly more educated and wealthier than most gay parents, Rosenfeld says.
"One of the fundamental issues in modern family law that differs from state to state is whether same-sex couples can adopt," Rosenfeld says in a statement. "My research makes clear that there's a huge advantage to kids to be out of the care of the state and into the care of any family, even if the family is not perfectly optimal."
Homosexuals with children are a small percentage of Americans, and designing a study with a suitable sample size has been difficult, Rosenfeld says.
"Sample size is power," Rosenfeld says. "And the census is the biggest sample we have. This study is based on a sample of thousands and thousands of kids."
The finding is published in the journal Demography.