Having a single mother doesn't appear to have a negative effect on the behavior or school performance of 12- and 13-year-olds, a new study says.

Cornell University researcher Henry Ricciuti said that the most important factors are a mother's education level and, to a lesser extent, family income and quality of the home. He found links between those maternal attributes and a child's school performance and behavior, whether the family was white, black or Hispanic.

He said the length of time living with a single parent didn't have an effect, either.

"Single parenthood in and of itself need not to be a risk factor for a child's performance in mathematics, reading or vocabulary or for behavior problems," Ricciuti said.

The study was a follow-up of children who were assessed when they were 6 and 7 years old. The first study, published in 1999, found that single parenthood did not affect young children's school readiness or social or behavioral problems.

Ricciuti's studied almost 1,500 12- and 13-year-old children from white, black and Hispanic families in the National Longitudinal Survey of Labor Market Experience of Youth.

Single motherhood was defined as the mother having no partner or spouse living at home at the time of the survey. The average mother's age at birth of her child was 20 to 21.

Ricciuti cautions that many single mothers lack the social, economic or parenting resources that are known to promote good parenting.