Oct. 22 (HealthDay News) -- Not only is secondhand smoke a threat to teen health, it can also affect their school test scores, a new study finds.

Researchers at Temple University found that 16- and 18-year-olds exposed to secondhand smoke at home were 30 percent less likely to pass standardized tests than their peers.

They reached this conclusion after analyzing data from thousands of mothers and children in the United Kingdom, and factoring in other known risk factors, such as socioeconomic status, gender and smoking by teens.

The study was published in the Journal of Adolescent Health.

The findings add to a growing body of evidence that secondhand smoke affects children's academic performance, as well as their health, the researchers said.

"It's important that we help smoking parents learn how to reduce their children's exposure to secondhand smoke, a goal that can be achieved without requiring the parent to immediately quit smoking, although that's the ultimate goal for the health of the entire family," study author Bradley Collins, an assistant professor of public health and director of the Health Behavior Research Clinic at Temple, said in a prepared statement.

This study did not answer why secondhand smoke affects teen's test scores. Previous studies have suggested a link between prenatal exposure to cigarette smoke and increased risk of cognitive and academic problems, learning disabilities and impulsivity in children.

SOURCE: Temple University, news release, September 2007