Some 23,000 children and young adults were asked about smoking and their home environment.
The study in the journal Pediatrics found exposure to secondhand smoke was linked to a 14-to-28 percent greater risk of poor school performance.
The findings do not prove smoke was the reason for the bad grades. But the researchers say it's possible that the many toxic compounds in tobacco smoke, including lead, arsenic and ammonia, could affect children's cognitive abilities.
